USB and Thunderbolt Optical Signal Transceiver

ABSTRACT

Systems and methods to implement a USB and Thunderbolt optical signal transceiver are described. One method includes detecting presence of a USB sideband signal received over an optical communication channel and associated with a USB communication request. Responsive to the detecting, the method may determine that the USB communication request corresponds to a USB communication mode and perform a sideband negotiation. The USB communication mode may be enabled. A specified number of channels associated with the USB communication request may be determined. USB communication may be performed using the specified number of channels over the optical communication channel in the USB communication mode.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Chinese Application Serial No.202110307189.9, filed Mar. 23, 2021, which is hereby incorporated hereinby reference in its entirety.

BACKGROUND Technical Field

The present disclosure relates to systems and methods that facilitatetransferring USB and Thunderbolt signals over optical communicationlinks.

Background Art

With the continuous development of computer technology, computerperipheral interface technology has entered the era of the universalserial bus (USB). Over its history, the USB interface unified thecomputer interface standard, from the era of PS/2, serial ports andparallel ports. USB, with its characteristics of plug and play and hightransmission speed, has quickly become a mainstream device interfacefavored by device manufacturers and users. The development of USBtechnology has progressed in stages, including USB1.0, USB2.0, USB3.0,USB3.1Gen, USB3.2 and USB4. Correspondingly, the data transfer rate ofthe USB protocol data transfer rates have increased from 1.5 Mbps, 12Mbps, 480 Mbps, 5 Gbps and 10 Gbps to 20 Gbps and 40 Gbps. In the era ofUSB1.0 and USB2.0, the USB protocol mainly used D+ and D− signals forhalf-duplex communication, with data transfer rates up to 480 Mbps.After the USB3.0 era, high-speed full-duplex communication channelsSuperSpeed Transmit (SSTX+/−) and SuperSpeed Receive (SSRX+/−) wereintroduced into USB, increasing data transfer rates to up to 5 Gbps.USB3.1 and USB3.2 further increased the data transfer rate to up to 10Gbps per channel. USB4 adopts the same physical interface as theThunderbolt protocol, which brings the single-channel data transfer rateup to 20 Gbps. In addition, USB3.2 and USB4 include a dual-channel formof the USB interface. In other words, these protocols implemented USB3.2Gen1x2, USB3.2 Gen2x2, USB4 Gen2x2 and USB4 Gen3x2. Theseimplementations essentially doubled the USB data transfer rate byimproving communication parallelism.

The Thunderbolt interface and protocol is a higher-speed IO standard.The Thunderbolt interface and protocol was designed to unify connectionsbetween computers and other devices. The development of Thunderbolt hasalso progressed in stages, including Thunderbolt, Thunderbolt 2,Thunderbolt 3 and Thunderbolt 4. Correspondingly, Thunderbolt protocoldata transfer rates have increased from 10 Gbps to 20 Gbps to 40 Gbps.Starting with Thunderbolt 3, Thunderbolt cable form factor was changedfrom a mini DisplayPort to USB type C. The Thunderbolt cable form factorchange significantly increased compatibility and unification with theUSB protocol.

From an implementation perspective, USB4 physical layer protocols andThunderbolt 3 physical layer protocols are very similar. As singlechannel data transfer rates for both the USB protocol and theThunderbolt protocol continue to increase, various shortcomings of thecommonly-used copper wire communication medium have been exposed. Ingeneral, when using copper wire, maintaining desired bit error rates andhigher quality data transfer becomes more difficult as data transferrates increase. For example, it can be difficult to maintain a 1e-12 biterror rate requirement of a physical layer protocol when data transferrates reach 20 Gbps and above. Additionally, it can be difficultmaintain long-distance, high-quality data transmission when datatransfer rates reach 5 Gbps and above.

A number of optical fiber techniques have attempted to address theshortfalls associated with implementing USB protocol data transfer andThunderbolt protocol data transfer over copper wire:

At least one technique uses an optical module (e.g., an integratedcircuit) to convert and transfer USB signals. Unfortunately, the datatransfer protocols utilized by the optical module generally define aspecific data transfer rate, for example, 10.3125 Gbps, 24.33 Gbps,25.78125 Gbps and 28.05 Gbps. An optical module with a data transferrate at or above 20 Gbps generally uses a clock data recovery circuit.However, 20 Gbps or higher rates are typically not within the workingrange of the optical module clock recovery circuit. In addition, anoptical module has a low integration level in terms of device footprint.Manufacturing active optical cables compatible with the USB andThunderbolt protocols is usually associated with a large volumemanufacturing capability and a high power consumption when manufacturingif an optical module is used.

At least one other technique, realizes photoelectric conversion ofsignals using a special transceiver chip within an optical module. Thetransceiver chip can be configured using an associated microcontroller.In this scheme, the optical module manufacturing is integrated into USBactive optical cable. The disadvantage is that the design of thecustomized integrated circuit (chip) for the optical module is generallycombined with single-channel reception and single channel transmission,or four-channels reception and four-channels transmission. There is noability to switch between the two modes. When using this chip to realizethe signal transmission of dual-channel USB protocol and Thunderboltprotocol, it is difficult to perform a patch and couple process duringmanufacturing. This makes the process complex and difficult to realize.In addition, in this scheme, sideband signals and channel configurationsignals need to be transmitted by extra copper wires.

SUMMARY

Aspects of the invention are directed to systems and methods fortransferring USB and Thunderbolt signals over optical communicationlinks.

One aspect includes detecting presence of a Universal Serial Bus (USB)sideband signal received over an optical communication channel andassociated with a USB communication request. Responsive to thedetecting, it is determined that the USB communication requestcorresponds to a USB communication mode. A sideband negotiation isperformed. The USB communication mode is enabled and a specified numberof channels associated with the USB communication request is determined.USB communication using the specified number of channels is performedover the optical communication channel in the USB communication mode.

Another aspect includes checking for but failing to detect a presence ofa USB sideband signal received over an optical communication channel.This other aspect also includes detecting presence of a low-frequencyperiodic signaling (LFPS) signal received over the optical communicationchannel and associated with a USB communication request. Responsive todetecting, it is determined that the USB communication requestcorresponds to a USB communication mode. Further responsive to thedetecting, an LFPS test is performed. The USB communication mode isenabled and a specified number of channels associated with the USBcommunication request are determined. USB communication using thespecified number of channels is performed over the optical communicationchannel in the USB communication mode.

Aspects include apparatus with electro-optical interfaces that implementthe described methods.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive embodiments of the present disclosureare described with reference to the following figures, wherein likereference numerals refer to like parts throughout the various figuresunless otherwise specified.

FIG. 1 is a block diagram depicting an embodiment of a USB opticalconnection interface.

FIG. 2 is a block diagram depicting an embodiment of an interfacebetween a USB system and an electro-optical interface.

FIG. 3 is a block diagram depicting an embodiment of an interfacebetween a USB system and an electro-optical interface.

FIG. 4 is a block diagram depicting an embodiment of an electro-opticalinterface.

FIG. 5 is a block diagram depicting an embodiment of an electro-opticalinterface.

FIG. 6 is a block diagram depicting an embodiment of a modulatingcircuit.

FIG. 7 is a block diagram depicting an embodiment of a demodulatingcircuit.

FIG. 8 is a block diagram depicting an embodiment of an LFPS signalmonitoring circuit.

FIG. 9 is a block diagram depicting an embodiment of a sideband signalmonitoring circuit.

FIG. 10 is a state flow diagram depicting a monitoring of sidebandsignals and channel configuration signals.

FIG. 11 is a circuit diagram depicting a modulating circuit.

FIG. 12 is a circuit diagram depicting a demodulating circuit.

FIG. 13 is a block diagram depicting an embodiment of a USB opticalconnection interface.

FIG. 14 is a block diagram depicting an embodiment of a USB opticalconnection interface.

FIG. 15 is an example flow diagram depicting a method to perform USBcommunication.

FIG. 16 is an example flow diagram depicting a method to perform USBcommunication.

FIG. 17 is an example flow diagram depicting a method to perform USBoptical communication.

DETAILED DESCRIPTION

In the following description, reference is made to the accompanyingdrawings that form a part thereof, and in which is shown by way ofillustration specific exemplary embodiments in which the disclosure maybe practiced. These embodiments are described in sufficient detail toenable those skilled in the art to practice the concepts disclosedherein, and it is to be understood that modifications to the variousdisclosed embodiments may be made, and other embodiments may beutilized, without departing from the scope of the present disclosure.The following detailed description is, therefore, not to be taken in alimiting sense.

Reference throughout this specification to “one embodiment,” “anembodiment,” “one example,” or “an example” means that a particularfeature, structure, or characteristic described in connection with theembodiment or example is included in at least one embodiment of thepresent disclosure. Thus, appearances of the phrases “in oneembodiment,” “in an embodiment,” “one example,” or “an example” invarious places throughout this specification are not necessarily allreferring to the same embodiment or example. Furthermore, the particularfeatures, structures, databases, or characteristics may be combined inany suitable combinations and/or sub-combinations in one or moreembodiments or examples. In addition, it should be appreciated that thefigures provided herewith are for explanation purposes to personsordinarily skilled in the art and that the drawings are not necessarilydrawn to scale.

Embodiments in accordance with the present disclosure may be embodied asan apparatus, method, or computer program product. Accordingly, thepresent disclosure may take the form of an entirely hardware-comprisedembodiment, an entirely software-comprised embodiment (includingfirmware, resident software, micro-code, etc.), or an embodimentcombining software and hardware aspects that may all generally bereferred to herein as a “circuit,” “module,” or “system.” Furthermore,embodiments of the present disclosure may take the form of a computerprogram product embodied in any tangible medium of expression havingcomputer-usable program code embodied in the medium.

Any combination of one or more computer-usable or computer-readablemedia may be utilized. For example, a computer-readable medium mayinclude one or more of a portable computer diskette, a hard disk, arandom-access memory (RAM) device, a read-only memory (ROM) device, anerasable programmable read-only memory (EPROM or Flash memory) device, aportable compact disc read-only memory (CDROM), an optical storagedevice, a magnetic storage device, and any other storage medium nowknown or hereafter discovered. Computer program code for carrying outoperations of the present disclosure may be written in any combinationof one or more programming languages. Such code may be compiled fromsource code to computer-readable assembly language or machine codesuitable for the device or computer on which the code can be executed.

Embodiments may also be implemented in cloud computing environments. Inthis description and the following claims, “cloud computing” may bedefined as a model for enabling ubiquitous, convenient, on-demandnetwork access to a shared pool of configurable computing resources(e.g., networks, servers, storage, applications, and services) that canbe rapidly provisioned via virtualization and released with minimalmanagement effort or service provider interaction and then scaledaccordingly. A cloud model can be composed of various characteristics(e.g., on-demand self-service, broad network access, resource pooling,rapid elasticity, and measured service), service models (e.g., Softwareas a Service (“SaaS”), Platform as a Service (“PaaS”), andInfrastructure as a Service (“IaaS”)), and deployment models (e.g.,private cloud, community cloud, public cloud, and hybrid cloud).

The flow diagrams and block diagrams in the attached figures illustratethe architecture, functionality, and operation of possibleimplementations of systems, methods, and computer program productsaccording to various embodiments of the present disclosure. In thisregard, each block in the flow diagrams or block diagrams may representa module, segment, or portion of code, which includes one or moreexecutable instructions for implementing the specified logicalfunction(s). It is also noted that each block of the block diagramsand/or flow diagrams, and combinations of blocks in the block diagramsand/or flow diagrams, may be implemented by special purposehardware-based systems that perform the specified functions or acts, orcombinations of special purpose hardware and computer instructions.These computer program instructions may also be stored in acomputer-readable medium that can direct a computer or otherprogrammable data processing apparatus to function in a particularmanner, such that the instructions stored in the computer-readablemedium produce an article of manufacture including instruction meanswhich implement the function/act specified in the flow diagram and/orblock diagram block or blocks.

Aspects of the invention described herein address various limitationsassociated with other communication techniques. Some embodimentsadaptive facilitating compatible transfer of Universal Serial Bus (USB)protocol signals and/or Thunderbolt protocol signals via an opticalfiber transmission system. Some embodiments include an appropriatemechanical coupling at each distal end of the optical fiber transmissionsystem (also referred to as an A-terminal interface and a B-terminalinterface). The optical fiber transmission system may utilize acombination of average optical power modulation and adaptive amplitudemodulation order switching. The combination can facilitate realizationof USB protocol signals and/or Thunderbolt protocol signals with smalloptical path overhead, and simultaneous transmission of sideband andchannel configuration (CC) signals.

The A-terminal interface and the B-terminal interface may be configuredwith monitoring units. Through the monitoring units, LFPS signals can bemonitored to obtain channel configuration signals or sideband signals,and a single-channel mode or a dual-channel mode adaptively selected.

In one aspect, the mode adaptive optical fiber transmission system iscompatible with a USB protocol and/or a Thunderbolt protocol at aphysical layer. As such, data format conversion between the USB protocoland the Thunderbolt protocol at a protocol layer is optional, andpossibly not needed. The mode adaptive optical fiber transmission systemmay be compatible with USB3.0, USB3.1 Gen1, USB3.1 Gen2, USB3.2 Gen1x2,USB3.2 Gen2, USB3.2 Gen2x2, USB4.0 and subsequent related USB protocols,Thunderbolt3, Thunderbolt4 and subsequent related Thunderbolt protocols.

Aspects include implementing at least two groups of bidirectionaloptical paths for signal transmission, with the physical layer beingadaptively compatible with single-channel and dual-channel USB protocolworking modes and Thunderbolt protocol working modes. In another morespecific aspect, signal transmission is implemented using a single groupof bidirectional optical paths. The physical layer may be adaptivelycompatible with the single-channel and dual-channel USB protocol workingmodes and Thunderbolt protocol working modes. In one aspect, theA-terminal interface and the B-terminal interface of an active opticalcable of the system are symmetrical, and the optical cable has nodirectionality.

FIG. 1 is a block diagram depicting an embodiment of a USB opticalconnection interface 100. As depicted, USB optical connection interface100 includes USB system 102, optical connector 122, and USB system 108.Optical connector 122 further includes electro-optical interface 104 andelectro-optical interface 106. Electro-optical interface 104 canoptically connect to electro-optical interface 106 via a bidirectionaloptical communication channel 110 and a bidirectional opticalcommunication channel 112. As depicted, bidirectional opticalcommunication channel 110 includes unidirectional optical communicationchannel 114 and unidirectional optical communication channel 116.Likewise, bidirectional optical communication channel 112 includesunidirectional optical communication channel 118 and unidirectionaloptical communication channel 120. In one aspect, optical connector 122may be referred to as a “mode adaptive optical fiber transmissionsystem.” USB system 102 may be referred to as an “A-terminal” and USBsystem 108 may be referred to as a “B-terminal.” Each of unidirectionaloptical communication channel 114, 116, 118 and 120 may be implementedusing one or more optical fibers.

In one aspect, each of USB system 102 and USB system 108 may be atand/or included within computing system that supports USB or Thunderboltcommunication. In this description and the following claims, a“computing system” is defined as a device that includes a processor,memory, and a communication interface. Each of USB system 102 and USBsystem 108 may be a USB device such as a USB camera, a USB hard drive, aUSB dongle, or any other device that supports USB connectivity.

In one aspect, electro-optical interface 104 is configured to receive afirst set of one or more USB or Thunderbolt electrical signals from USBsystem 102. Electro-optical interface 104 may convert these USB orThunderbolt electrical signals to a corresponding set of USB orThunderbolt optical signals. Electro-optical interface 104 may transmitthese USB or Thunderbolt optical signals via any combination ofunidirectional optical communication channel 114 and/or unidirectionaloptical communication channel 118 to electro-optical interface 106.Electro optical interface 106 may receive these USB or Thunderboltoptical signals and convert these USB or Thunderbolt optical signalsinto a corresponding second set of USB or Thunderbolt electricalsignals. This second set of USB or Thunderbolt electrical signals may besubstantially identical to the first set of USB or Thunderboltelectrical signals received by electro-optical interface 104 from USBsystem 102. Electro-optical interface 106 may then transmit the secondset of USB or Thunderbolt electrical signals to USB system 106.

In one aspect, electro-optical interface 106 is configured to receive athird set of one or more USB or Thunderbolt electrical signals from USBsystem 108. Electro-optical interface 106 may convert these USB orThunderbolt electrical signals to a corresponding set of USB orThunderbolt optical signals. Electro-optical interface 106 may transmitthese USB or Thunderbolt optical signals via any combination ofunidirectional optical communication channel 116 and unidirectionaloptical communication channel 120 to electro-optical interface 104.Electro optical interface 104 may receive these USB or Thunderboltoptical signals and convert these USB or Thunderbolt optical signalsinto a corresponding fourth set of USB or Thunderbolt electricalsignals. This fourth set of USB or Thunderbolt electrical signals may besubstantially identical to the third set of USB or Thunderboltelectrical signals received by electro-optical interface 106 from USBsystem 108. Electro-optical interface 104 may then transmit the secondset of USB or Thunderbolt electrical signals to USB system 102.

In the following description, the following abbreviations are defined:

SSTX: USB SuperSpeed Transmit

SSRX: USB SuperSpeed Receive

SBTX: USB Sideband Transmit

SBRX: USB Sideband Receive

CC: USB Configuration Channel

LFPS: USB Low-Frequency Periodic Signaling

FIG. 2 is a block diagram depicting an embodiment of an interface 200between USB system 102 and electro-optical interface 104. As depicted,USB system 102 includes SSTX0+/−terminal 202, SSTX1+/−terminal 204,SSRX0+/−terminal 206, SSRX1+/−terminal 208, SBTX terminal 210, CCterminal 212, and SBRX terminal 214. Electro-optical interface 104includes SSTX0+/−terminal 216, SSTX1+/−terminal 218, SSRX0+/−terminal220, SSRX1+/−terminal 222, SBTX terminal 224, CC terminal 226, and SBRXterminal 228. Electro-optical interface 104 also includeselectro-optical conversion 230, photoelectric conversion 232,electro-optical conversion 234, and photoelectric conversion 236.

In one aspect, SSTX0+/−terminal 202 through SBRX terminal andSSTX0+/−terminal 216 through SBRX terminal 228 facilitate transmittingand receiving USB protocol signals and/or Thunderbolt protocol signals.SSTX0+/−terminal 202 may transmit an SSTX0+/−differential USB electricalsignal to SSTX0+/−terminal 216. SSTX1+/−terminal 204 may transmit anSSTX1+/−differential USB electrical signal to SSTX1+/−terminal 218.SSRX0+/−terminal 206 may receive an SSRX0+/−differential USB electricalsignal from SSRX0+/−terminal 220. SSRX1+/−terminal 208 may receive anSSRX1+/−differential USB electrical signal from SSRX1+/−terminal 222.SBTX terminal 210 may transmit an SBTX USB sideband electrical signal toSBTX terminal 224. SBRX terminal 214 may receive an SBRX USB sidebandelectrical signal from SBRX terminal 228. CC terminal 212 and CCterminal 226 may bidirectionally communicate USB CC data.

In one aspect, the SSTX0+/−differential USB electrical signal, theSSTX1+/−differential USB electrical signal, the SBTX USB electricalsignal, and one or more CC electrical signals may be respectivelyconverted into an SSTX0+/−differential USB optical signal, anSSTX1+/−differential USB optical signal, an SBTX USB optical signal, andone or more CC optical signals by any combination of electro-opticalconversion 230 and electro-optical conversion 234. In one aspect, eachof electro-optical conversion 230 and 234 is configured to convert oneor more electrical signals into a corresponding set of optical signals.Each of electro-optical conversion 230 and 234 can include one or more(e.g., arrays of) laser diodes such as vertical-cavity surface-emittinglasers (VCSELs).

In one aspect, electro-optical conversion 230 outputs one or more outputsignals converted from electrical signals via unidirectional opticalcommunication channel 114. These output signals may be transmitted viaunidirectional optical communication channel 114 to electro-opticalinterface 106. Electro-optical conversion 234 may output one or moreoutput signals converted from electrical signals via unidirectionaloptical communication channel 118. These output signals may betransmitted via unidirectional optical communication channel 118 toelectro-optical interface 106.

In one aspect, each of photoelectric conversion 232 and photoelectricconversion 236 receives one or more optical signals from electro-opticalinterface 106 over unidirectional optical communication channel 116 andunidirectional optical communication channel 120, respectively. Theseoptical signals may be any combination of an SSRX0+/−optical signal, anSSRX1+/−optical signal, an SBRX optical signal, and one or more CCoptical signals. Each of photoelectric conversion 232 and photoelectricconversion 236 may be comprised of one or more (e.g., arrays of)photodiodes or photodetectors.

Each of photoelectric conversion 232 and photoelectric conversion 236may convert the received optical signals to any combination of anSSRX0+/−USB differential electrical signal, an SSRX1+/−USB differentialelectrical signal, an SSRX USB electrical signal, and one or more CCelectrical signals. These electrical signals correspond to their opticalcounterparts. These signals are transmitted from electro-opticalinterface 104 to USB system 102 via the appropriate terminals. In oneaspect, the SSRX0+/−USB differential electrical signal is transmittedfrom SSRX0+/−terminal 220 to SSRX0+/−terminal 206; the SSRX1+/−USBdifferential electrical signal is transmitted from SSRX1+/−terminal 222to SSRX1+/−terminal 208; the SBRX USB electrical signal is transmittedfrom SBRX terminal 228 to SBRX terminal 214, and CC terminal 212 and CCterminal 226 bidirectionally communicate USB CC electrical signals.

FIG. 3 is a block diagram depicting an embodiment of an interface 300between USB system 108 and electro-optical interface 106. As depicted,USB system 108 includes SSTX0+/−terminal 324, SSTX1+/−terminal 326,SSRX0+/−terminal 328, SSRX1+/−terminal 330, SBTX terminal 332, CCterminal 334, and SBRX terminal 336. Electro-optical interface 106includes SSTX0+/−terminal 310, SSTX1+/−terminal 312, SSRX0+/−terminal314, SSRX1+/−terminal 316, SBTX terminal 318, CC terminal 320, and SBRXterminal 322. Electro-optical interface 106 also includes anelectro-optical conversion 304, a photoelectric conversion 302, anelectro-optical conversion 308, and a photoelectric conversion 306.

In one aspect, SSTX0+/−terminal 324 through SBRX terminal 336 on USBsystem and SSTX0+/−terminal 310 through SBRX terminal 322 onelectro-optical interface 106 are associated with transmitting andreceiving the associated USB protocol or Thunderbolt protocol signals.SSTX0+/−terminal 324 may transmit an SSTX0+/−differential USB electricalsignal to SSTX0+/−terminal 310. SSTX1+/−terminal 326 may transmit anSSTX1+/−differential USB electrical signal to SSTX1+/−terminal 312.SSRX0+/−terminal 328 may receive an SSRX0+/−differential USB electricalsignal from SSRX0+/−terminal 314. SSRX1+/−terminal 330 may receive anSSRX1+/−differential USB electrical signal from SSRX1+/−terminal 316.SBTX terminal 332 may transmit an SBTX USB sideband electrical signal toSBTX terminal 318. SBRX terminal 336 may receive an SBRX USB sidebandelectrical signal from SBRX terminal 322. CC terminal 334 and CCterminal 320h may bidirectionally communicate USB CC data.

In one aspect, the SSTX0+/−differential USB electrical signal, theSSTX1+/−differential USB electrical signal, the SBTX USB electricalsignal, and one or more CC electrical signals may be respectivelyconverted into an SSTX0+/−differential USB optical signal, anSSTX1+/−differential USB optical signal, an SBTX USB optical signal, andone or more CC optical signals by any combination of electro-opticalconversion 304 and electro-optical conversion 308. In one aspect, eachof electro-optical conversion 304 and 308 is configured to convert oneor more electrical signals into a corresponding set of optical signals.In one embodiment, each of electro-optical conversion 304 and 308 iscomprised of one or more (e.g., arrays of) laser diodes such asvertical-cavity surface-emitting lasers (VCSELs).

In one aspect, electro-optical conversion 304 outputs one or more outputsignals converted from electrical signals via unidirectional opticalcommunication channel 116. These output signals may be transmitted viaunidirectional optical communication channel 116 to electro-opticalinterface 104. Electro-optical conversion 308 may output one or moreoutput signals converted from electrical signals via unidirectionaloptical communication channel 120. These output signals may betransmitted via unidirectional optical communication channel 120 toelectro-optical interface 104.

In one aspect, each of photoelectric conversion 302 and photoelectricconversion 306 receives one or more optical signals from electro-opticalinterface 104 over unidirectional optical communication channel 114 andunidirectional optical communication channel 118, respectively. Theseoptical signals may be any combination of an SSRX0+/−optical signal, anSSRX1+/−optical signal, an SBRX optical signal, and one or more CCoptical signals. Each of photoelectric conversion 302 and photoelectricconversion 306 may be comprised of one or more (e.g., arrays of)photodiodes or photodetectors.

Each of photoelectric conversion 302 and photoelectric conversion 306may convert the received optical signals to any combination of anSSRX0+/−USB differential electrical signal, an SSRX1+/−USB differentialelectrical signal, an SSRX USB electrical signal, and one or more CCelectrical signals. These electrical signals correspond to their opticalcounterparts. These signals are transmitted from electro-opticalinterface 106 to USB system 108 via the appropriate terminals. In oneaspect, the SSRX0+/−USB differential electrical signal is transmittedfrom SSRX0+/−terminal 314 to SSRX0+/−terminal 328; the SSRX1+/−USBdifferential electrical signal is transmitted from SSRX1+/−terminal 316to SSRX1+/−terminal 330; the SBRX USB electrical signal is transmittedfrom SBRX terminal 322 to SBRX terminal 336, and CC terminal 320 and CCterminal 334 bidirectionally communicate USB CC electrical signals.

Referring back to FIG. 1, optical connector 122 can be implemented as amode adaptive optical fiber transmission system compatible with USBprotocol signals and/or Thunderbolt protocol signals. In one aspect,optical connector 122 includes an A-terminal interface and a B-terminalinterface, implemented as electro-optical interface 104 and/orelectro-optical interface 106. Since optical connector 122 isdirectionally independent with respect to connectivity, electro-opticalinterface 104 is an A-terminal interface and electro-optical interface106 is a B-terminal interface in one configuration. In anotherconfiguration, electro-optical interface 106 is an A-terminal interfaceand electro-optical interface 104 is a B-terminal interface.

The active optical cable realized by optical connector 122 may include asymmetrical structure at both terminals, with no master-slaverelationship and no directionality with respect to physical connections.In other words, optical connector may be reversed such thatelectro-optical interface 106 is connected to USB system 102, andelectro-optical interface 104 is connected to USB system 108.

When connecting single-channel transmission devices, for example,USB3.0, USB3.1, etc. devices, using optical connector 122, either ofbidirectional optical communication channel 110 or 112 may be enabled.In this case, the other bidirectional optical communication channel(i.e., bidirectional optical communication channel 112 or 110,respectively) can be disabled. Disabling a communication channel canconserve power.

When connecting two-channel transmission devices, for example, USB3.2Gen1x2, USB3.2 Gen2x2, USB4.0 Gen2x2, USB4.0 Gen3x2, Thunderbolt 3,Thunderbolt 4, etc. devices using optical connector 122, bothbidirectional optical communication channels 110 and 112 can be enabledto carry out dual-channel transmission. In one aspect, the originalseven electrical interfaces associated with the USB or Thunderboltprotocols (i.e., SSTX0+/−, SSTX1+/−, SBRX0+/−, SBRX1+/−, SBTX, SBRX, andCC interfaces) are compressed into two or four optical interfaces (i.e.,using either of bidirectional optical communication channels 110 or 112,or using both bidirectional optical communication channels 110 and 112).This compressing enables realizing optical fiber transmission(communication) relatively with low complexity, high integration, lowpower consumption, low cost as compared to contemporary solutions, whilemaintaining compatibility with USB3, USB4 and Thunderbolt protocols.

In one aspect, optical connector 122 is compatible with the USB protocoland Thunderbolt protocol in an associated physical layer, and does notneed to carry out data format conversion between the USB protocol andthe Thunderbolt protocol in a protocol layer. Examples of data formatconversion include descrambling and decoding any received data, and thenre-encoding and re-scrambling the data. Since optical connector 122operates on a physical layer, such data format conversions are notneeded.

Optical connector 122 is generally applicable to USB3.0, USB3.1 Gen1,USB3.1 Gen2, USB3.2 Gen1x2, USB3.2 Gen2, USB3.2 Gen2x2, USB4.0 andsubsequent related USB protocols, Thunderbolt3, Thunderbolt4, andsubsequent related Thunderbolt protocols.

In one aspect, the A-terminal interface and the B-terminal interface(e.g., electro-optical interfaces 104 and 106 respectively, orelectro-optical interface 106 and 104 respectively) associated withoptical connector 122 implements a combination of average optical powermodulation and adaptive amplitude modulation order switching to realizehigh-speed signals of the USB protocol and the Thunderbolt protocol witha relatively small optical path overhead. This combination of averageoptical power modulation and adaptive amplitude modulation orderswitching enables optical connector 122 to simultaneously transmitsideband and channel configuration (CC) signals.

In one aspect, the A-terminal interface and B-terminal interfaceassociated with optical connector 122 are configured with one or moremonitoring units that are configured monitor LFPS signals to obtainchannel configuration signals or sideband signals, and adaptively selectsingle-channel mode or dual-channel mode.

In one aspect, optical connector 122 implements a high-speed signaltransmission mode and a low-speed signal transmission mode consisting ofsideband signals and passband configuration signals. According todifferent high-speed signal transmission modes, the functionality ofoptical connector 122 can be any one of a four-optical-fibertransmission mode and a two-optical-fiber transmission mode.

Moving to FIG. 4, FIG. 4 is a block diagram depicting an embodiment ofan electro-optical interface 400. Electro-optical interface 400 may beused to implement either or both of electro-optical interface 104 andelectro-optical interface 106. Electro-optical interface 400 may supporttwo bidirectional optical communication channels.

As depicted, electro-optical interface 400 includes interface 402, laserbias current modulator 418, monitoring unit 420, time divisionmultiplexing unit 422, multiplexer 424, time division demultiplexingunit 426, average optical power detection circuit 434, time divisiondemultiplexing unit 432, average optical power detection circuit 430,laser bias current modulator 428, TX circuit 436, TX circuit 438, RXcircuit 440, and RX circuit 442. Interface 402 further includesSSTX0+/−terminal 404 (that may be similar to SSTX0+/−terminal 216 or310), SSTX1+/−terminal 406 (that may be similar to SSTX1+/−terminal 218or 312), SSRX0+/−terminal 408 (that may be similar to SSRX0+/−terminal220 or 314), SSRX1+/−terminal 410 (that may be similar toSSRX1+/−terminal 222 or 316), SBTX terminal 412 (that may be similar toSBTX terminal 224 or 318), CC terminal 414 (that may be similar to CCterminal 226 or 320), and SBRX terminal 416 (that may be similar to SBRXterminal 228 or 322).

In one aspect, interface 402 is a mechanical interface that is used toconnect electro-optical interface 400 to a USB system such as USB system102 or 108. Terminals SSTX0+/−404 through SBRX 416 electrically connectto the corresponding SSTX0+/−through SBRX terminals of the connected USBsystem.

In one aspect, SSTX0+/− and SSTX1+/−(USB differential electrical)signals are received from the connected USB system by SSTX0+/−terminal404 and SSTX1+/−terminal 406, respectively. The SSTX0+/− andSSTX1+/−signals are respectively transmitted from SSTX0+/−terminal 404and SSTX1+/−terminal 406 to laser bias current modulator 418 and laserbias current modulator 428, respectively. These SSTX0+/− andSSTX1+/−signals may be high-speed differential USB communicationsignals.

In one aspect, laser bias current modulator 418 converts the electricalSSTX0+/−signal into an optical SSTX0+/−signal. Laser bias currentmodulator 428 may convert the electrical SSTX1+/−signal into an opticalSSTX1+/−signal.

In one aspect, SBTX terminal 412 receives one or more SBTX USB sideband(electrical) signals from the connected USB system.

In one aspect, CC terminal 414 receives one or more CC USB (electrical)signals from the connected USB system. These CC USB signals aretransmitted to time division multiplexing unit 422.

In one embodiment, time division multiplexing unit 422 time-divisionmultiplexes the SBTX USB sideband signals and the CC USB signals togenerate a multiplexed electrical signal. This multiplexed electricalsignal may be used to bias each of laser bias current modulator 418 andlaser bias current modulator 428. In this way, the SBTX USB sidebandsignals and the CC USB signals may be used to modulate an average powerlevel of each of the optical SSTX0+/−signal and the opticalSSTX1+/−signal. Laser bias current modulator 418 outputs a laser biascurrent signal with an average power that is modulated by thetime-division multiplexed SBTX USB sideband signals and the CC USBsignal. Laser bias current modulator 428 outputs a laser bias currentsignal with an average power that is modulated by the time-divisionmultiplexed SBTX USB sideband signals and the CC USB signal.

The laser bias current signal output from laser bias current modulator418 is received by TX circuit 436. TX circuit 436 converts this signalinto an optical signal and transmits the optical signal over aunidirectional optical communication channel 444. The laser bias currentsignal output from laser bias current modulator 428 is received by TXcircuit 438. TX circuit 438 converts this signal into an optical signaland transmits the optical signal over a unidirectional opticalcommunication channel 446. Each of TX circuit 436 and 438 may be acircuit configured to convert one or more electrical signals intocorresponding optical signals, and may be similar in form and functionto any of electro-optical conversion 230, electro-optical conversion234, electro-optical conversion 304, and electro-optical conversion 308.Each of TX circuit 436 and 438 may be comprised of one or more (e.g.,arrays of) VCSELs.

If electro-optical interface 400 functions similar to electro-opticalinterface 104, then TX circuit 436 functions similar to electro-opticalconversion 230, and TX circuit 438 functions similar to electro-opticalconversion 234. Unidirectional optical communication channels 444 and446 correspond to unidirectional optical communication channels 114 and118, respectively. The SSTX0+/− and SSTX1+/−optical signals modulated bySBTX USB sideband signals and CC USB signals are transmitted overunidirectional optical communication channels 444/114 and 446/118respectively, to electro-optical interface 106, where these signals arereceived as SSRX0+/− and SSRX1+/−optical signals modulated by SBRX USBsideband signals and CC USB signals.

If electro-optical interface 400 functions similar to electro-opticalinterface 106, then TX circuit 436 functions similar to electro-opticalconversion 304, and TX circuit 438 functions similar to electro-opticalconversion 308. Unidirectional optical communication channels 444 and446 correspond to unidirectional optical communication channels 116 and120, respectively. The SSTX0+/− and SSTX1+/−optical signals modulated bySBTX USB sideband signals and CC USB signals are transmitted overunidirectional optical communication channels 444/116 and 446/120respectively, to electro-optical interface 104, where these signals arereceived as SSRX0+/− and SSRX1+/−optical signals modulated by SBRX USBsideband signals and CC USB signals.

In one aspect, electro-optical interface 400 receives one or moreoptical signals via unidirectional optical communication channels 448and 450. Electro-optical interface 400 may receive a combination of anSSRX0+/−USB optical differential signal, one or more SBRX USB opticalsignals, and one or more CC USB optical signals, via unidirectionaloptical communication channel 448. Electro-optical interface 400 mayreceive a combination of an SSRX1+/−USB optical differential signal, oneor more SBRX USB optical signals, and one or more CC USB opticalsignals, via unidirectional optical communication channel 450.

The optical signals received over unidirectional optical communicationchannel 448 may be received by RX circuit 440. The optical signalsreceived over unidirectional optical communication channel 450 may bereceived by RX circuit 442. In one aspect, each of RX circuit 440 and442 may be configured to convert any received optical signals tocorresponding electrical signals. Each of RX circuit 440 and 442 may becomprised of one or more (e.g., arrays of) photodetectors.

In one aspect, RX circuit 440 converts a received SSRX0+/−USB opticaldifferential signal into an SSRX0+/−USB electrical differential signalthat is transmitted from RX circuit 440 to SSRX0+/−terminal 408.SSRX0+/−terminal 408 may transmit the SSRX0+/−USB electricaldifferential signal to a connected USB system (e.g., USB system 102 or108).

In one aspect, RX circuit 442 converts a received SSRX1+/−USB opticaldifferential signal into an SSRX1+/−USB electrical differential signalthat is transmitted from RX circuit 442 to SSRX1+/−terminal 410.SSRX0+/−terminal 410 may transmit the SSRX0+/−USB electricaldifferential signal to a connected USB system (e.g., USB system 102 or108).

In one aspect, average optical power detection circuit 430 extracts anaverage optical power from the SSRX0+/−optical differential signal asreceived by RX circuit 440. Average optical power detection circuit 430may extract one or more SBRX USB electrical signals and one or more CCUSB electrical signals from the average optical power, and transmit theSBRX USB electrical signals and CC electrical USB signals to timedivision demultiplexing unit 432. Time division demultiplexing unit 432may be configured to demultiplex the SBRX USB electrical signals and CCUSB electrical signals, and transmit these signals to multiplexer 424.

In one aspect, average optical power detection circuit 434 extracts anaverage optical power from the SSRX1+/−optical differential signal asreceived by RX circuit 442. Average optical power detection circuit 434may extract one or more SBRX USB electrical signals and one or more CCUSB electrical signals from the average optical power, and transmit theSBRX USB electrical signals and CC USB electrical signals to timedivision demultiplexing unit 426. Time division demultiplexing unit 426may be configured to demultiplex the SBRX USB electrical signals and CCUSB electrical signals, and transmit these signals to multiplexer 424.

In one aspect, multiplexer 424 multiplexes and appropriately routes theSBRX USB electrical signals and the CC USB electrical signals receivedfrom time division demultiplexing units 426 and 432, to CC terminal 414and SBRX terminal 416 respectively. These signals may then betransmitted by electro-optical interface 404 to a connected USB system(e.g., USB system 102 or 108).

When electro-optical interface 400 functions similar to electro-opticalinterface 104, then RX circuit 440 functions similar to photoelectricconversion 232, and RX circuit 442 functions similar to photoelectricconversion 236. Unidirectional optical communication channels 448 and450 correspond to unidirectional optical communication channels 116 and120, respectively. The SSRX0+/− and SSRX1+/−optical signals modulated bySBTX USB sideband signals and CC USB signals are received overunidirectional optical communication channels 448/116 and 450/120respectively, from electro-optical interface 106, where these signalsare transmitted as SSTX0+/− and SSTX+/−optical signals modulated by SBTXUSB sideband signals and CC USB signals, respectively.

When electro-optical interface 400 functions similar to electro-opticalinterface 106, then RX circuit 440 functions similar to photoelectricconversion 302, and RX circuit 442 functions similar to photoelectricconversion 306. Unidirectional optical communication channels 448 and450 correspond to unidirectional optical communication channels 114 and118, respectively. The SSRX0+/− and SSRX1+/−optical signals modulated bySBTX USB sideband signals and CC USB signals are received overunidirectional optical communication channels 448/114 and 450/118respectively, from electro-optical interface 104, where these signalsare transmitted as SSTX0+/− and SSTX+/−optical signals modulated by SBTXUSB sideband signals and CC USB signals, respectively.

In one aspect, monitoring unit 420 monitors each of the SSTX0+/−USBdifferential electrical signal at SSTX0+/−terminal 404, the SSTX1+/−USBdifferential electrical signal at SSTX1+/−terminal 406, the SSRX0+/−USBdifferential electrical signal at SSRX0+/−terminal 408, the SSRX1+/−USBdifferential electrical signal at SSRX1+/−terminal 410, the STBX USBelectrical signals at SBTX terminal 412, the SBRX USB electrical signalat SBRX terminal 416, and the CC USB electrical signals at CC terminal414 to determine a negotiation result of LFPS signals in high-speedsignals during USB3 signal transmission. This monitoring enableselectro-optical interface 400 to obtain channel configurationinformation associated with USB communication being performed by opticalconnector 122. When LFPS negotiation shows that single-channelcommunication is needed, SSTX1+/−, SSRX1+/− and related circuits (i.e.,laser bias current modulator 428, TX circuit 438, RX circuit 422,average optical power detection circuit 434, and time divisionmultiplexing unit 426) are powered down, thereby reducing cable powerconsumption in the single-channel communication mode.

Referring again back to FIG. 1, in one aspect, optical connector 122implements a four-optical-fiber transmission structure. As depicted inFIG. 1, optical connector 122 uses two groups of bidirectional opticalpaths (i.e., bidirectional optical communication channels 110 and 112)in a four-optical-fiber configuration. Optical connector 122 may beadaptive to a single-channel or a dual-channel working mode compatiblewith the USB protocol and the Thunderbolt protocol. The A-terminalinterface (e.g., electro-optical interface 104) of optical connector 122may be symmetrical with the B-terminal interface (e.g., electro-opticalinterface 106). In other words, optical connector has no directionalitywith respect to connection.

At each port (i.e., electro-optical interface 104 and 106), high-speedsignals SSTX0+/− and SSTX1+/− may be transferred to two lasers fortransmission, and two receiving circuits receive the high-speed signalsat the opposite terminal and output them to their own terminals SSRX0+/−and SSRX1+/−. In one aspect, optical connector 112 uses clock recoverycircuit to resample a received signal.

A device A (e.g., USB system 102) is connected to the terminal A (e.g.,electro-optical interface 104) and a device B (e.g., USB system 108) isconnected to the terminal B (e.g., electro-optical interface 106). TheA-terminal interface and the B-terminal interface are configured as atransmitting terminal and a receiving terminal. The transmittingterminal modulates sideband signals and channel configuration signalsinto the same optical path as high-speed signals for transmissionthrough time division multiplexing and laser bias current modulation.The receiving terminal uses an average optical power detection circuitto separate low-speed signals and demultiplex and drive the sidebandsignals and channel configuration signals of the opposite end.

In one aspect, the high-speed signals SSTX0+/− and SSTX1+/− at theterminal A are modulated to two different transmitting circuits (e.g.,electro-optical conversion 230 and electro-optical conversion 234)respectively. These high-speed signals are then converted into opticalsignals through photoelectric conversion and transmitted to the terminalB through two optical fibers. After electro-optical conversion andprocessing the received signal through two different receiving circuits(e.g., photoelectric conversion 304 and 308), terminal B demodulates thehigh-speed signals from the modulated optical signals and transmits themto two pins (terminals) SSRX0+/− and SSRX1+/− at the terminal B.

At the same time of high-speed signal transmission at terminal A,sideband signal (SBTX) and channel configuration signal (CC) aremodulated on the bias current of the laser after time divisionmultiplexing, and the average optical power is modulated on the outputoptical signal of the laser. The adjusted optical signal is transmittedto the terminal B through the optical path, then the low-speed signal isdemodulated by the average optical power detection circuit at theterminal B. The sideband signal and channel configuration signal aredecomposed by the time division multiplexing unit and transmitted to theSBRX pin and CC pin at the terminal B.

The high-speed signals SSTX0+/− and SSTX1+/− at the terminal B aremodulated to two different transmitting circuits respectively, and thenconverted into optical signals through photoelectric conversion (e.g.,using electro-optical conversion 304 and 308) and transmitted to theterminal A through two optical fibers (e.g., unidirectional opticalcommunication channels 116 and 120). After electro-optical conversionand processing the received signal through two different receivingcircuits (e.g., photoelectric conversion 232 and 236), the terminal Ademodulates the high-speed signals from the modulated optical signalsand transmits them to two pins SSRX0+/− and SSRX1+/− at the terminal A.

The sideband signal (SBTX) and channel configuration signal (CC) at theterminal B are modulated on the bias current of the laser after timedivision multiplexing, and the average optical power is modulated on theoutput optical signal of the laser. The adjusted optical signal istransmitted to the terminal A through the optical path, then thelow-speed signal is demodulated by the average optical power detectioncircuit of the terminal A, and then the sideband signal and channelconfiguration signal are decomposed by the time division multiplexingunit and transmitted to the SBRX pin and CC pin of the terminal A.

In one aspect, when an adaptive channel associated with opticalconnector 122 is closed and the single channel communicates is enabled,and portions of optical connector 122 associated with the disabledchannel are switched off. At this time, the power consumption isapproximately half of the power consumption associated with dual-channelcommunication. In this configuration, SSTX1+/−, SSRX1+/− and relatedcircuits are turned on when the LFPS negotiation result of USB3 showsthat the system is dual-channel communication. In the definition of theUSB4 protocol the sideband signal is used for channel configuration, sowhen sideband the signal is transmitted, a monitoring unit 420associated with each of electro-optical interfaces 104 and 106adaptively selects the working mode by acquiring the channelconfiguration of terminal A and terminal B, and shuts down the relevantchannel in single channel mode to save power consumption.

Turning now to FIG. 5, FIG. 5 is a block diagram depictingelectro-optical interface 500. Electro-optical interface 500 may be usedto implement either or both of electro-optical interface 104 andelectro-optical interface 106. Electro-optical interface 500 may supporta single bidirectional optical communication channel comprised of twoindividual unidirectional optical communication channels.

As depicted, electro-optical interface 500 includes interface 502,PAM4/NRZ modulating unit 518, laser bias current modulator 520, PAM4/NRZdemodulating unit 522, monitoring unit 526, time division multiplexingunit 524, time division demultiplexing unit 528, average optical powerdetection circuit 530, TX circuit 532, and RX circuit 534. Interface 502further includes SSTX0+/−terminal 504 (that may be similar toSSTX0+/−terminal 216 or 310), SSTX1+/−terminal 506 (that may be similarto SSTX1+/−terminal 218 or 312), SSRX0+/−terminal 508 (that may besimilar to SSRX0+/−terminal 220 or 314), SSRX1+/−terminal 510 (that maybe similar to SSRX1+/−terminal 222 or 316), SBTX terminal 512 (that maybe similar to SBTX terminal 224 or 318), CC terminal 514 (that may besimilar to CC terminal 226 or 320), and SBRX terminal 516 (that may besimilar to SBRX terminal 228 or 322).

In one aspect, electro-optical interface 500 is configured to transmitand receive any combination of 4-level pulse-amplitude modulated (PAM4)signals or non-return to zero (NRZ) signals.

In one aspect, interface 502 is a mechanical interface that is used toconnect electro-optical interface 500 to a USB system such as USB system102 or 108. Terminals SSTX0+/−504 through SBRX 516 electrically connectto the corresponding SSTX0+/−through SBRX terminals of the connected USBsystem.

In one aspect, SSTX0+/− and SSTX1+/− (USB differential electrical)signals are received from the connected USB system by SSTX0+/−terminal504 and SSTX1+/−terminal 506, respectively. The SSTX0+/− andSSTX1+/−signals are respectively transmitted from SSTX0+/−terminal 504and SSTX1+/−terminal 506 to PAM4/NRZ modulating unit 518. These SSTX0+/−and SSTX1+/−signals may be high-speed differential USB communicationsignals.

In one aspect, PAM4/NRZ modulating unit 518 combines the electricalSSTX0+/− and SSTX1+/−electrical signals into a composite PAM4 electricalsignal. This operation occurs when electro-optical interface operates ina two-channel communication mode. In a single-channel communicationmode, only an SSTX0+/−electrical signal is received by electro-opticalinterface 500. In PAM4/NRZ modulating unit 518 modulates theSSTX0+/−electrical signal into an NRZ electrical signal. Laser biascurrent modulator 428 may convert the PAM4 or NRZ electrical signaloutput by PAM4/NRZ modulating unit 518 into an optical PAM4 or NRZoptical signal, respectively.

In one aspect, SBTX terminal 512 receives one or more SBTX USB sideband(electrical) signals from the connected USB system. These SBTX USBsideband signals are transmitted to time division multiplexing unit 524.

In one aspect, CC terminal 514 receives one or more CC USB (electrical)signals from the connected USB system. These CC USB signals aretransmitted to time division multiplexing unit 524.

In one embodiment, time division multiplexing unit 524 time-divisionmultiplexes the SBTX USB sideband signals and the CC USB signals togenerate a multiplexed electrical signal. This multiplexed electricalsignal may be used to bias laser bias current modulator 520. In thisway, the SBTX USB sideband signals and the CC USB signals may be used tomodulate an average power level of the PAM4 optical signal or NRZoptical signal (depending on the mode of communication).

Laser bias current modulator 520 outputs a laser bias current signalwith an average power that is modulated by the time-division multiplexedSBTX USB sideband signals and the CC USB signal. Laser bias currentmodulator 520 outputs a laser bias current signal with an average powerthat is modulated by the time-division multiplexed SBTX USB sidebandsignals and the CC USB signal.

The laser bias current signal output from laser bias current modulator520 is received by TX circuit 532. TX circuit 532 converts this signalinto an optical signal and transmits the optical signal over aunidirectional optical communication channel 536. In one aspect, TXcircuit 532 is a circuit configured to convert one or more electricalsignals into corresponding optical signals, and may be similar in formand function to any of electro-optical conversion 230, electro-opticalconversion 234, electro-optical conversion 304, and electro-opticalconversion 308. TX circuit 532 may be comprised of one or more (e.g.,arrays of) VCSELs.

If electro-optical interface 500 functions similar to electro-opticalinterface 104, then TX circuit 532 may function similar toelectro-optical conversion 230. Unidirectional optical communicationchannel 536 may correspond to unidirectional optical communicationchannels 114. The SSTX0+/−optical signal or the combination of theSSTX0+/− and SSTX1+/−optical signals (depending on transmission mode),modulated by SBTX USB sideband signals and CC USB signals, aretransmitted over unidirectional optical communication channel 536/114,to electro-optical interface 106, where these signals are received asSSRX0+/− and SSRX1+/−optical signals modulated by SBRX USB sidebandsignals and CC USB signals, respectively.

If electro-optical interface 500 functions similar to electro-opticalinterface 106, then TX circuit 532 may function similar toelectro-optical conversion 304. Unidirectional optical communicationchannel 536 may correspond to unidirectional optical communicationchannels 116. The SSTX0+/−optical signal or the combination of theSSTX0+/− and SSTX1+/−optical signals (depending on the USB communicationmode being used by electro-optical interface 500), modulated by SBTX USBsideband signals and CC USB signals, are transmitted over unidirectionaloptical communication channel 536/116, to electro-optical interface 104,where these signals are received as SSRX0+/− and SSRX1+/−optical signalsmodulated by SBRX USB sideband signals and CC USB signals, respectively.

In one aspect, electro-optical interface 500 receives one or moreoptical signals via unidirectional optical communication channel 538.Electro-optical interface 500 may receive a combination of an SSRX0+/−and an SSRX1+/−USB optical differential signal or an SSRX0+/−USB opticaldifferential signal (depending on the USB communication mode being usedby electro-optical interface 500), one or more SBRX USB optical signals,and one or more CC USB optical signals, via unidirectional opticalcommunication channel 538.

The optical signals received over unidirectional optical communicationchannel 538 may be received by RX circuit 534. In one aspect, RX circuit534 may be configured to convert any received optical signals tocorresponding electrical signals. RX circuit 538 may be comprised of oneor more (e.g., arrays of) photodetectors.

In a two-channel communication mode, RX circuit 534 may convert areceived PAM4 optical signal into a PAM4 electrical signal. This PAM4electrical signal may be comprised of an SSRX0+/−USB differentialsignal, an SSRX1+/−USB differential signal, an SBRX USB signal, and oneor more CC USB signals. In one aspect, PAM4/NRZ demodulating unit 522may extract an SSRX0+/−USB electrical differential signal and anSSRX1+/−USB electrical differential signal from the PAM4 electricalsignal. PAM4/NRZ demodulating unit 522 may transmit the SSRX0+/−USBelectrical differential signal and the SSRX1+/−USB electricaldifferential signal to SSRX0+/−terminal 508 and SSRX1+/−terminal 510,respectively. SSRX0+/−terminal 508 and SSRX1+/−terminal 510 mayrespectively transmit the SSRX0+/−USB electrical differential signal andthe SSRX1+/−USB electrical differential signal to a connected USB system(e.g., USB system 102 or 108).

In a single-channel communication mode, RX circuit 534 may convert areceived NRZ optical signal into a NRZ electrical signal. This NRZelectrical signal may be comprised of an SSRX0+/−USB differentialsignal, an SBRX USB signal, and one or more CC USB signals. In oneaspect, PAM4/NRZ demodulating unit 522 may extract an SSRX0+/−USBelectrical differential signal from the NRZ electrical signal. PAM4/NRZdemodulating unit 522 may transmit the SSRX0+/−USB electricaldifferential signal to SSRX0+/−terminal. SSRX0+/−terminal 508 maytransmit the SSRX0+/−USB electrical differential signal to a connectedUSB system (e.g., USB system 102 or 108).

In one aspect, average optical power detection circuit 530 extracts anaverage optical power from the PAM4 or NRZ optical signal as received byRX circuit 534. Average optical power detection circuit 530 may extractone or more SBRX USB electrical signals and one or more CC USBelectrical signals from the average optical power, and transmit the SBRXUSB electrical signals and CC electrical USB signals to time divisiondemultiplexing unit 528. Time division demultiplexing unite 532 may beconfigured to demultiplex the SBRX USB electrical signals and CC USBelectrical signals, and transmit these signals to SBRX terminal 516 andCC terminal 514, respectively. SBRX terminal 616 and CC terminal 514 mayrespectively transmit the SBRX USB electrical signals and the CC USBelectrical signals to a connected USB system (e.g., USB system 102 or108).

If electro-optical interface 500 functions similar to electro-opticalinterface 104, then RX circuit 534 functions similar to photoelectricconversion 232. Unidirectional optical communication channel 538corresponds to unidirectional optical communication channel 116. ThePAM4 or NRZ optical signal modulated by SBTX USB sideband signals and CCUSB signals are received over unidirectional optical communicationchannel 448/116, from electro-optical interface 106.

If electro-optical interface 400 functions similar to electro-opticalinterface 106, then RX circuit 534 functions similar to photoelectricconversion 302. Unidirectional optical communication channel 538corresponds to unidirectional optical communication channel 114. ThePAM4 or NRZ optical signal modulated by SBTX USB sideband signals and CCUSB signals are received over unidirectional optical communicationchannels 448/114, from electro-optical interface 104.

In one aspect, monitoring unit 526 monitors each of the SSTX0+/−USBdifferential electrical signal, the S STX1+/−USB differential electricalsignal, SSRX0+/−USB differential electrical signal, the S SRX1+/−USBdifferential electrical signal, the STBX USB electrical signals, theSBRX USB electrical signal, and the CC USB electrical signals todetermine a negotiation result of LFPS signals in high-speed signalsduring USB3 signal transmission. This enables electro-optical interface500 to obtain channel configuration information associated with USBcommunication being performed by optical connector 122. When LFPSnegotiation shows that single-channel communication is needed, SSTX1+/−,SSRX1+/− and related circuits are powered down, thereby reducing cablepower consumption in the single-channel communication mode. In oneaspect, a single- or dual-channel communication configuration in USBB 4or Thunderbolt mode is determined based on monitoring sidebandnegotiation (e.g., LFPS sideband negotiation).

In one aspect, optical connector 122 uses one group of bidirectionaloptical paths (i.e., two optical fibers) for signal transmission. Inthis case, each of electro-optical interface 104 and 106 has a structuresimilar to electro-optical interface 500. In this configuration, opticalconnector 122 may be adaptive to the single-channel and dual-channelworking modes compatible with USB protocol and the Thunderbolt protocol.The A-terminal interface (e.g., electro-optical interface 104) of activeoptical cable is symmetrical with the B-terminal interface (e.g.,electro-optical interface 106), and the optical cable has nodirectionality.

At each port (i.e., electro-optical interface 104 or 106), high-speedsignals SSTX0+/−, SSTX1+/− may be modulated into the same laser (e.g.,as included in TX circuit 532) for transmission. In dual-channelcommunication, two high-speed signals are modulated into PAM4 signals,while in single-channel communication, high-speed signals aretransmitted by NRZ coding. The receiving terminal selects PAM4demodulation or NRZ demodulation according to channel configuration(i.e., subsequent to decoding CC USB communication signals) and thenoutputs them to its own SSRX0+/−, SSRX1+/−terminals. In one aspect, eachelectro-optical interface included in optical connector 122 uses a clockrecovery circuit to extract the clock from the output of the thresholddecider in the middle of the signal, and resamples the signal with theextracted clock signal.

Particularly, high-speed signals SSTX0+/− and SSTX1+/− at terminal A aremodulated to the same transmitting circuit by PAM4, and then convertedinto optical signals by photoelectric conversion and transmitted toterminal B through an optical fiber. After passing through theelectro-optical conversion and PAM4 receiving circuit, the signals areconverted into two NRZ signals SSRX0+/− and SSRX1+/− by PAM4demodulation unit and transmitted to terminal B. Same as the four-fibertransmission method, in the two-optical-fiber transmission method, theout-of-band signal and the channel configuration signal are modulated bythe laser bias current, and demodulated by the average optical powerdetection when receiving. B-terminal high-speed signals SSTX0+/−,SSTX1+/are modulated to the same transmitting circuit by PAM4, and thenconverted into optical signals through photoelectric conversion and PAM4receiving circuit, and then the signals are converted into two NRZsignals, SSRX0+/− and SSRX1+/−, through PAM4 demodulation unit andtransmitted to A-terminal. A detection unit 1 and a detection unit 2(each of which may be similar to monitoring unit 526) use the monitoringresults of LFPS signals or sideband signals at the A and B terminals todetermine the channel configuration, respectively. PAM4 codingmodulation and demodulation is selected in the dual-channelconfiguration, and NRZ coding modulation and demodulation is selected inthe single-channel configuration, and some circuits are turned off atthe same time to save power consumption.

FIG. 6 is a block diagram depicting an embodiment of a modulatingcircuit 600. As depicted, modulating circuit 600 includesSSRX0+/−terminal 602, SSTX0+/−terminal 604, SBTX terminal 606, SBRXterminal 608, SSTX1+/−terminal 610, SSRX1+/−terminal 612, low-passfilter LPF 614, low-pass filter LPF 634, low-pass filter LPF 616,low-pass filter LPF 636, buffer B 618, buffer B 638, clock data recoveryunit 620, clock data recovery unit 628, LFPS detection circuit 622, LFPSdetection circuit 640, selection switch 626, selection switch 630,sampling unit 624, sampling unit 632, monitoring unit 642, channelenabling unit 644, channel enabling unit 646, 2:1 weighted additioncircuit 648, linear laser drive circuit 650, and laser 652.

Modulating circuit may be implemented in electro-optical interface 500and may perform adaptive PAM4/NRZ modulation functions depending onchannel configuration. In one aspect, SSRX0+/−terminal 602 correspondsto SSRX0+/−terminal 508, SSTX0+/−terminal 604 corresponds toSSTX0+/−terminal 504, SBTX terminal 606 corresponds to SBTX terminal512, SBRX terminal 608 corresponds to SBRX terminal 516,SSTX1+/−terminal 610 corresponds to SSTX1+/−terminal 506, andSSRX1+/−terminal 612 corresponds to SSRX1+/−terminal 510. Monitoringunit 642 may correspond to monitoring unit 526.

In one aspect, an SSRX0+/−USB differential electrical signal received atSSRX0+/−terminal 602 is low-pass filtered by LPF 614 and transmitted toLFPS detection circuit 622. An SSRX1+/differential electrical signalreceived at SSRX1+/−terminal 612 is low-pass filtered by LPF 634 andtransmitted to LFPS detection circuit 640.

In one aspect, an SSTX0+/−USB differential electrical signal atSSTX0+/−terminal 604 is transmitted to:

LPF 616 that low-pass filters the SSTX0+/−USB differential electricalsignal and transmits the filtered signal to LFPS detection circuit 622,

Buffer B 618 that amplifies the SSTX0+/−USB differential electricalsignal and transmits the amplified signal to sampling unit 624, and

Clock data recovery unit 620 that performs clock data recover on theSSTX0+/−USB differential electrical signal.

In one aspect, an SSTX1+/−USB differential electrical signal atSSTX1+/−terminal 610 is transmitted to:

LPF 636 that low-pass filters the SSTX1+/−USB differential electricalsignal and transmits the filtered signal to LFPS detection circuit 640,

Buffer B 636 that amplifies the SSTX1+/−USB differential electricalsignal and transmits the amplified signal to sampling unit 632, and

Clock data recovery unit 628 that performs clock data recover on theSSTX1+/−USB differential electrical signal.

An SBTX USB electrical signal at SBTX terminal 606 and an SBRX signal atSBRX terminal 608 may both be transmitted to monitoring unit 642.

In one aspect, modulating circuit 600 implements adaptive PAM4/NRZmodulation uses the circuit structure of the transmitting part whenusing a single bidirectional optical communication channel that uses twooptical fibers. An example of such an implementation is electro-opticalinterface 500.

In one aspect, clock and data recovery unit 620 is used to recover aclock signal from the input high-speed signal (i.e., the SSTX0+/−USBdifferential electrical signal at SSTX0+/−terminal 604), and therecovered clock signal is used to resample the signal. The recoveredclock unit as output by clock data recovery unit 620 in a single-channelconfiguration may only drive sampling 624 to sample the data of theSSTX0+/−USB differential electrical signal. The recovered clock signalas output by clock data recovery unit 620 in a dual-channelconfiguration may drive sampling unit 624 and sampling unit 632 at thesame time, and may be used to sample signals of terminals SSTX0+/−604and SSTX1+/−610 at the same time.

In one aspect, clock data recovery unit 628, selection switch 626, andselection switch 630 are used to provide redundant logic for the clockrecovery circuit to improve the fault tolerance of the circuit. This isdone by recovering a clock signal from the SSTX1+/−USB differentialelectrical signal at SSTX1+/−terminal 610. The two clock signals outputby clock data recovery units 620 and 628 are multiplexed by selectionswitches 626 and 630, to sampling units 624 and 632, respectively.

After sampling, the output signals of sampling unit 624 and samplingunit 632 may be transmitted to channel enabling unit 644 and channelenabling unit 646, respectively. Each of channel enabling unit 644 and646 may be controlled by an output of monitoring unit 642. Monitoringunit 642 may be configured to independently enable or disable each ofchannel enabling unit 644 and 646 depending on how an SBTX USBelectrical signal from SBTX terminal 606, an SBRX USB electrical signalfrom SBRX terminal 608, an output from LFPS detection circuit 622, andan output from LFPS detection circuit 640 are processed. Each of LFPSdetection circuit 622 and LFPS detection circuit 624 determines whetherUSB sideband signals are present in the respective input signals. Basedon this determination, LFPS detection circuits 622 and 624 independentlydetermine whether a dual-channel mode or a single-channel mode isenabled. In one aspect, each of LFPS detection circuit 622 and 640 maybe implemented as a filter and an envelope detector.

If monitoring unit 642 determines that a two-channel mode is enabled,both channel enabling units 642 and 646 may be enabled. In thedual-channel mode, the outputs of channel enabling units 644 and 646 arereceived by 2:1 weighted addition circuit 648. 2:1 weighted additioncircuit 648 performs a weighting and addition on the two input signalsto generate a PAM4 modulation electrical signal. Linear laser drivecircuit 650 conditions this PAM4 modulation electrical signal andoutputs the conditioned PAM4 electrical signal to laser 652 (e.g., aVCSEL). Laser 652 converts the conditioned PAM4 electrical signal to aPAM4 optical signal 656 that is transmitted over an appropriate opticalcommunication channel (e.g., unidirectional optical communicationchannel 536). In the dual-channel mode, SSTX0+/− and SSTX1+/−USB signalsare transmitted at the same time via PAM4 optical signal 656.

If monitoring unit 642 determines that a single-channel mode is enabled,components of modulating circuit 600 that support a second channel maybe turned off to conserve power. In one aspect, SBTX1+/−terminal 610,SSRX1+/−terminal 612, clock data recovery unit 628, buffer 638, low passfilters 634 and 636, LFPS detection circuit 640, sampling unit 632,selection switch 630, and channel enabling unit 646 are turned off inthe single-channel mode. In the single-channel mode, the output ofchannel enabling unit 644 is received by 2:1 weighted addition circuit648. 2:1 weighted addition circuit 648 generates an NRZ modulationelectrical signal based on this input. Linear laser drive circuit 650conditions this NRZ modulation electrical signal and outputs theconditioned NRZ electrical signal to laser 652 (e.g., a VCSEL). Laser652 converts the conditioned NRZ electrical signal to a NRZ opticalsignal 654 that is transmitted over an appropriate optical communicationchannel (e.g., unidirectional optical communication channel 536).

FIG. 7 is a block diagram depicting an embodiment of a demodulatingcircuit 700. As depicted, demodulating circuit 700 includesSSRX0+/−terminal 702, SSTX0+/−terminal 704, SBTX terminal 706, SBRXterminal 708, SSTX1+/−terminal 710, SSRX1+/−terminal 712, low-passfilter LPF 714, low-pass filter LPF 724, low-pass filter LPF 716,low-pass filter LPF 722, buffer B 718, buffer BB 720, LFPS detectioncircuit 736, decoding circuit 734, LFPS detection circuit 726, samplingunit 732, clock data recovery unit 730, sampling unit 728, monitoringunit 738, sampling unit 740, threshold decider 742, threshold decider744, threshold decider 748, automatic gain amplifier 752, lineartransimpedance (TIA) amplifier 750, and photodetector PD 754.

Demodulating circuit 700 may be implemented in electro-optical interface500 and may perform adaptive PAM4/NRZ demodulation functions dependingon channel configuration. In one aspect, SSRX0+/−terminal 702corresponds to SSRX0+/−terminal 508, SSTX0+/−terminal 704 corresponds toSSTX0+/−terminal 504, SBTX terminal 706 corresponds to SBTX terminal512, SBRX terminal 708 corresponds to SBRX terminal 516,SSTX1+/−terminal 710 corresponds to SSTX1+/−terminal 506, andSSRX1+/−terminal 712 corresponds to SSRX1+/−terminal 510.

In one aspect, photodetector PD 754 receives an optical signal over anoptical communication channel such as unidirectional opticalcommunication channel 114 or 118 (if demodulating circuit is integratedinto electro-optical interface 106), or unidirectional opticalcommunication channel 116 or 120 (if demodulating circuit is integratedinto electro-optical interface 104). Photodetector PD 754 converts thereceived optical signal into an electrical current signal that is thenamplified by linear TIA 750. Linear TIA 750 amplifies the electricalcurrent signal into a differential voltage signal. Automatic gainamplifier 752 may perform further amplification on the differentialvoltage signal and transmit the amplified differential voltage signal tothreshold deciders 742, 744 and 748.

If demodulating circuit 700 operates in a two-channel communicationmode, a combination of threshold deciders 742, 744 and 748 may deriveamplitude coding information from the amplified differential voltagesignal to extract a PAM4 modulation electrical signal 756 from theamplified differential voltage signal. In one aspect, this extraction isperformed relative to a threshold level a, a threshold level b, and athreshold level c, as indicated in PAM4 modulation electrical signal756. In general, threshold level c>threshold level b>threshold level awith respect to amplitude values. In one aspect, the decision thresholdsa, b and c are between numerical values of 2 and 3, 1 and 2, and 0 and 1respectively. These numerical values may be associated with PAM4modulation electrical signal 756.

If demodulating circuit operates in a one-channel communication mode,then threshold deciders 742, 744 and 748 may derive amplitude codinginformation from the amplified differential voltage signal generated byautomatic gain amplifier 752, to extract an NRZ electrical signal 758.In one aspect, this extraction is performed relative to threshold levelb as indicated in NRZ electrical signal 758. The threshold level b maybe approximately midway between numerical values of 0 and 3. Thesenumerical values may be associated with NRZ electrical signal 758.

In one aspect, outputs generated by threshold decider 742, 744, and 748are transmitted to sampling unit 740, 732, and 728, respectively. Theoutput generated by threshold decider 744 may also be transmitted toclock data recovery unit 730 that performs clock data recovery optionson the received data. Each of sampling units 740, 732 and 728 mayperform sampling on the respective input signal(s) referenced to a clocksignal output by clock data recovery unit 730.

In one aspect, output signals generated by each of sampling units 740,732 and 738 are received by decoding unit 734. Decoding unit 734 mayextract SSRX0+/− and SSRX1+/−signals from the received signals. TheSSRX0+/−signal may be transmitted from decoding unit 734 to buffer B 718that amplifies the SSRX0+/−signal and transmits the amplified SSRX0+/−(differential electrical) signal to SSRX0+/−terminal 702. TheSSRX1+/−signal may be transmitted from decoding unit 734 to buffer B 720that amplifies the SSRX1+/−signal and transmits the amplified SSRX1+/−(differential electrical) signal to SSRX1+/−terminal 712.

In one aspect, LPF 714, 716, 722, and 724 function similar to LPF 614,616, 636, and 634, respectively. Outputs of LPF 714 and 716 may bereceived by LFPS detection circuit 736. Outputs of LPF 722 and 724 maybe received by LFPS detection circuit 726. Each of LFPS detectioncircuit 736 and 726 may be configured to perform LFPS signal detectionon the received signals. Each of LFPS detection circuit 736 and LFPSdetection circuit 726 determines whether USB sideband signals arepresent in the respective input signals. Based on this determination,LFPS detection circuits 736 and 726 independently determine whether adual-channel mode or a single-channel mode is enabled.

In one aspect, monitoring unit 738 receives signals from LFPS detectioncircuits 736 and 726, and from SBTX terminal 706 and SBRX terminal 708.Monitoring unit 738 may be configured to control decoding circuit 734and sampling unit 732 depending on how an SBTX USB electrical signalfrom SBTX terminal 706, an SBRX USB electrical signal from SBRX terminal708, an output from LFPS detection circuit 736, and an output from LFPSdetection circuit 726 are processed.

In one aspect, if monitoring unit 738 detects a one-channel (i.e.,single-channel) configuration, sampling unit 732 uses only thresholdlevel b to sample the input signal. In the one-channel configuration,decoding unit 734 may decode an associated USB high-speed communicationsignal as an NRZ signal. If monitoring unit 738 detects a two-channelconfiguration, all three threshold levels—a, b, and c may be used. Inthe one-channel configuration, decoding unit 734 may decode anassociated USB high-speed communication signal as a PAM4 signal.

In one aspect, demodulating circuit 700 may be integrated intoelectro-optical interface 500. In this implementation, the photoelectricdetector (i.e., photodetector PD 754) performs electro-opticalconversion to convert the received optical signal into current. Thelinear transimpedance amplifier (i.e., linear TIA 750) converts thecurrent into a differential voltage signal, and the automatic gaindeveloper (i.e., automatic gain amplifier 752) adjusts the signalamplitude to a certain value.

In one aspect, the received signal is PAM4 signal in dual-channeloperation mode, and the output of the automatic gain amplifier obtainssignal amplitude coding information through threshold decider 742,threshold decider 744 and threshold decider 748 as shown in the PAM4 eyediagram (i.e., PAM4 modulation electrical signal 756). As shown in thisPAM4 eye diagram, threshold a>threshold b>threshold c. If the associatedPAM4 signal amplitude is 0, 1, 2 and 3, the decision thresholds a, b andc are between 2 and 3, 1 and 2 and 0 and 1 respectively.

In one aspect, the output signal of threshold decider 744 is extractedby clock data recovery unit 730, and the obtained clock signal drivessampling unit 732. Sampling unit 740, sampling unit 732, and samplingunit 728 respectively synchronously sample the outputs of thresholddecider 742, threshold decider 744, and threshold decision 748. Theoutputs of the three samplers (i.e., sampling units 740, 732 and 728)constitute a three-bit thermometer code. When the input signal is 3,then 3>a, 3>b, 3>c, so the outputs of three sampling circuits are “111”,“011” when the input signal is 2, and “001” and “000” when the inputsignals are 1 and 0 respectively.

In one aspect, decoding circuit 734 converts the thermometer code into a2-bit binary code. The binary signal output by decoding circuit 734 maydrive SSRX0+/− and SSRX1+/−terminals 702 and 712, respectively, throughbuffers 718 and 720.

Modulating circuit 700 may be configured to operate in a single-channelcommunication mode. In this mode, the signal received by photodetector754 is an NRZ signal. It can be seen from NRZ eye diagram (i.e., NRZelectrical signal 758) that only the threshold determiner b is used tooutput the determinable signal level. In the single-channel operationmode, only a portion of demodulating circuit 700 may be activated, withother portions of this circuit being powered down. For example, in asingle-channel communication mode, photodetector 754, linear TIA 750,automatic gain amplifier 752, threshold decider 744, clock data recoveryunit 730, sampling unit 732, decoding circuit 734, LFPS detectioncircuit 736, LPF 714 and 716, buffer 718, and SSRX0+/−terminal 702,SSTX0+/−terminal 704, SBTX terminal 706, and SBRX terminal 708 areactivated, with the other components of demodulating circuit 700 beingpowered down. The above-mentioned single-channel or dual-channeloperation mode is judged by monitoring unit 738 by monitoring thesideband signal and the LFPS signal.

FIG. 8 is a block diagram depicting an embodiment of an LFPS signalmonitoring circuit 800. As depicted, LFPS signal monitoring circuit 800includes SSRX0+/−terminal 802, SSTX0+/−terminal 804, low pass filter LPF806, low pass filter LPF 808, envelope length detection 810, envelopelength detection 814, idle time detection 812, idle time detection 816,LFPS instruction lookup table 818, and LFPS instruction lookup table820. LFPS signal monitoring circuit 800 may be used to implement any,some, or all of LSPF detection circuits 622, 640, 726, and 736.

In one aspect, SSRX0+/−terminal 802 and SSTX0+/−terminal 804 mayrespectively correspond to SSRX0+/−terminal 408 and SSTX0+/−terminal404, or SSRX0+/−terminal 508 and SSTX0+/−terminal 504.

In one aspect, an SSRX0+/−USB differential electrical signal atSSRX0+/−terminal 802 is transmitted to LPF 806. The SSRX0+/−USBdifferential electrical signal may be comprised of a USB high-speedsignal and one or more low-speed USB signals. LPF 806 may be configuredto filter out the high-frequency components (i.e., the USB high-speedsignal), and pass through the low-speed USB signals. In one aspect, thelow-speed USB signals include one or more LFPS signals. The bandwidth ofLPF 806 may be set to 50 MHz.

In one aspect, an output of LPF 806 is received by envelope lengthdetection 810 and idle time detection 812. Envelope length detection 810and idle time detection 812 may be configured to extract two maindecision elements, burst time and repeat time, from the filteredSSRX0+/−USB differential electrical signal. In one aspect, the bursttime and repeat time are received by LFPS instruction lookup table 818.LFPS instruction lookup table 818 may be configured to determine apresence of one or more of a polling signal, an SCD1 signal, an SCD2signal, and an LBPM signal associated with the SSRX0+/−USB differentialelectrical signal. This presence may be determined by using a burst timeand repeat time look-up table included in LFPS instruction lookup table818.

In one aspect, an SSTX0+/−USB differential electrical signal atSSTX0+/−terminal 804 is transmitted to LPF 808. The SSTX0+/−USBdifferential electrical signal may be comprised of a USB high-speedsignal and one or more low-speed USB signals. LPF 808 may be configuredto filter out the high-frequency components (i.e., the USB high-speedsignal), and pass through the low-speed USB signals. In one aspect, thelow-speed USB signals include one or more LFPS signals. The bandwidth ofLPF 808 may be set to 50 MHz.

In one aspect, an output of LPF 808 is received by envelope lengthdetection 814 and idle time detection 816. Envelope length detection 814and idle time detection 816 may be configured to extract two maindecision elements, burst time and repeat time, from the filteredSSTX0+/−USB differential electrical signal. In one aspect, the bursttime and repeat time are received by LFPS instruction lookup table 820.LFPS instruction lookup table 818 may be configured to determine apresence of one or more of a polling signal, an SCD1 signal, an SCD2signal, and an LBPM signal associated with the SSRX0+/−USB differentialelectrical signal. This presence may be determined by using a burst timeand repeat time look-up table included in LFPS instruction lookup table820.

In one aspect, an LFPS signal monitoring circuit 800 is used for signalmonitoring, power-on enumeration, rate negotiation and jump control of aLink Training and Status State Machine (LTSSM) during USB3 signaltransmission. A special LBPM signal is added to USB3.2, in which asingle channel or a dual channel control configuration is defined.Therefore, the channel configuration of USB3 can be obtained bymonitoring one or more LFPS signals output by LPF 806 and/or LFP 808.

At the same time, LFPS signals at both terminals may be monitored byLFPS signal monitoring circuit 800 to judge the negotiation results ofdevices at both sides. When one terminal only has polling signalsinstead of SCD1 and SCD2 signals during LFPS negotiation, it means thatan associated USB device (e.g., USB system 102 or 108) is a USB3.0device and only supports single channel mode.

If both communication parties (e.g., USB system 102 and 108) use SCD1and SCD2 signals for negotiation, it means that each of the associatedUSB device (i.e., each of USB system 102 and 108) is a USB3.1 or USB3.2device. LFPS signal monitoring circuit 800 may further analyze an LBPMsignal; if the LBPM signal only contains rate information but does notcontain channel configuration information, then each USB device is aUSB3.1 device, and communication is in a single channel mode.

If LBPM information contains channel configuration information, LFPSsignal monitoring circuit 800 may analyze negotiation of channelconfiguration information at both terminals. Based on this analysis, aconfiguration of the party with low channel number in negotiation istaken as the channel configuration.

When each USB device (e.g., USB system 102 and 108) is a USB4 device,there is no LFPS signal in the high-speed channel. When a USB3 adapterexists in USB4, the LFPS signal is converted into a special packet fortransmission. The channel configuration negotiation of USB4 is mainlyconducted through sideband communication.

FIG. 9 is a block diagram depicting an embodiment of a sideband signalmonitoring circuit 900. As depicted, sideband signal monitoring unit 900includes SBTX terminal 902, SBRX terminal 904, amplifier AMP 906,amplifier AMP 908, sideband packet analysis 910, sideband packetanalysis 912, and sideband register space read/write monitoring 914.Sideband signal monitoring circuit 900 may be used to implement any,some, or all of monitoring units 420, 526, 642, and 738.

In one aspect, the sideband signal monitoring unit 900 monitors thesideband signals of the transmitting USB terminal and the receiving USBterminal at the same time to judge the channel configuration negotiationresult of both terminals.

In one aspect, an SBTX signal at SBTX terminal 902 is amplified by AMP906, and received by sideband packet analysis 910. Sideband packetanalysis 910 may be configured to analyze a sideband packet contained inthe SBTX signal to obtain a resolution of the associated sidebandcommunication. An output of sideband packet analysis 910 may betransmitted to sideband register space read/write monitoring 914.

In one aspect, an SBRX signal at SBRX terminal 904 is amplified by AMP908, and received by sideband packet analysis 912. Sideband packetanalysis 912 may be configured to analyze a sideband packet contained inthe SBRX signal to obtain a resolution of the associated sidebandcommunication. An output of sideband packet analysis 912 may betransmitted to sideband register space read/write monitoring 914.

In one aspect, sideband register space read/write monitoring 914analyzes signals from sideband packet analysis 910 and 912, and extractsthe read-write information of channel configuration related registers inthe associated sideband signal packet. Based on the extraction, sidebandregister space read/write monitoring 914 may obtain an associatedchannel configuration negotiation result, with the lowest channel numberin both terminals of communication as the channel negotiation result.

In one aspect, sideband register space read/write monitoring 914monitors the sideband signals of SBTX terminal 902 and SBRX terminal 904at the same time to judge the channel configuration negotiation resultof both terminals.

FIG. 10 is a state flow diagram 1000 depicting a monitoring of sidebandsignals and channel configuration signals. In one aspect, the state flowreceives an initialization USB signal 1016 and enters an initializationstate 1002. From the initialization state, the state flow 1000 performstransition 1018 and transitions to a sideband signal detection state1004. In the sideband signal detection state 1004, state flow 1000analyzes the associated USB communication to determine a presence of oneor more sideband signals in the USB signals.

If state flow 1000 detects one or more sideband signals, then the stateflow undergoes transition 1022 to a sideband negotiation state 1006. Thepresence of a sideband signal indicates that USB4 communication is beingperformed. In sideband negotiation state 1006, state flow 1000 mayperform a sideband negotiation to determine whether the associated USBcommunication is a single-channel USB communication or a dual-channelUSB communication.

If sideband negotiation state 1006 determines that single-channelcommunication is being performed, then state flow 1000 performstransition 1028 to a single-channel configuration state 1014, wheredual-channel USB4 communication may be performed.

If sideband negotiation state 1006 determines that dual-channelcommunication is being performed, then state flow 1000 performstransition 1026 to a dual-channel configuration state 1012, wheredual-channel USB4 communication may be performed.

If sideband negotiation state 1006 determines that a communication errorhas occurred, then state flow 1000 may perform transition 1024 toinitialization state 1002 for re-monitoring.

In one aspect, if state 1004 does not detect a sideband signal, thenstate flow 1000 performs transition 1020 to an LFPS signal detectionstate 1008. The absence of a sideband signal may indicate that USB3communication is being performed. In one aspect, LFPS signal detectionstate 1008 may be an LFPS signal test state. This state may includetesting the existence of one or more LFPS signals in the USBcommunication signals. This enables state flow 1000 to distinguishbetween an LFPS signal and a high-speed USB communication signal.

Once LFPS signal detection state 1008 completes all the associatedfunctions, state flow 1000 may perform transition 1030 to an LFPS signaldetection state 1010. In one aspect, LFPS signal detection state 1010 isan LFPS snooping state. In this state one or more LFPS signals on boththe transmit (TX) and receive (RX) sides are checked to determine anegotiation result between the two sides. Based on this, LFPS signaldetection state 1010 determines whether the associated USB communicationis a single-channel USB communication or a dual-channel USBcommunication.

If LFPS signal detection state 1010 determines that single-channelcommunication is being performed, then state flow 1000 performstransition 1032 to single-channel configuration state 1014, wheredual-channel USB3 communication (or communication that uses an earlierUSB protocol) may be performed.

If LFPS signal detection state 1010 determines that dual-channelcommunication is being performed, then state flow 1000 performstransition 1034 to single-channel configuration state 1012, wheredual-channel USB3 communication (or communication that uses an earlierUSB protocol) may be performed.

If LFPS signal detection state 1010 determines that a communicationerror has occurred, then state flow 1000 may perform transition 1036 toinitialization state 1002 for re-monitoring.

In general, state flow diagram 1000 depicts a functionality of asideband signal and channel configuration signal monitoring statemachine. When the associated USB device is plugged in, the sidebandsignal and channel configuration signal monitoring state machine detectsthe sideband signal first, and if there is a sideband signal, monitorsthe sideband signal negotiation, and decides whether the configurationis single channel or dual channel. In one aspect, this functionality isimplemented using sideband signal monitoring circuit 900.

If there is no sideband signal, LFPS negotiation monitoring isperformed. In one aspect, the channel of USB3 is configured as a singlechannel or a dual channel according to the negotiation monitoring. Ifthere are data errors and other abnormalities in the monitoring process,the process returns to the initialization state for re-monitoring. Inone aspect, this functionality is implemented using LFPS signalmonitoring circuit 800.

State flow diagram 1000 may be implemented on any of electro-opticalinterface 104, 106, 400, or 500. Specifically, elements of state flowdiagram may be implemented using a combination of an LFPS detectioncircuit (e.g., 622, 640, 726, or 736) and a monitoring unit (e.g., 642or 738).

FIG. 11 is a circuit diagram depicting a modulating circuit 1100.Modulating circuit may be configured to modulate low-speed signals ontoUSB high-speed signals. As depicted, modulating circuit 1100 includesSSTX0+/−terminal 1102, high-speed signal modulation circuit 1106, laserdriving circuit 1110, laser bias control 1112, laser diode 1114, andbuffer 1108.

SSTX0+/−terminal 1102 may be similar to SSTX0+/−terminal 202 or 324. AnSSTX0+/−high-speed USB differential electrical signal received atSSTX0+/−terminal 1102 is transmitted to high-speed signal modulationcircuit 1106. High-speed signal modulation circuit 1106 may transmit ahigh-speed NRZ electrical signal 1118 corresponding to theSSTX0+/−high-speed USB differential electrical signal, to laser drivingcircuit 1110.

In one aspect, a low-speed electrical signal 1104 is amplified by buffer1108 to generate a low-speed amplified electrical signal 1120. Low-speedelectrical signal 1104 may be comprised of one or more signals,including USB sideband and USB CC signals. Low-speed amplifiedelectrical signal 1120 is input to laser bias current control 1112.Laser bias current control 1112 uses low-speed amplified electricalsignal 1120 to modulate an average power of high-speed NRZ electricalsignal 1118 via laser driving circuit 1110. Laser driving circuit 1110may modulate the average power of high-speed NRZ electrical signal 1118using the output of laser bias current control (based on low-speedamplified electrical signal 1120), to generate a composite electricalsignal output. This composite electrical signal may be converted into anoptical signal by laser diode 1114 to generate an optical NRZ signal1122 that has an average optical power level 1124 in accordance withlow-speed signal 1104. In one aspect, laser diode 1114 is a VCSEL.

In one aspect, optical NRZ signal 1122 is transmitted via aunidirectional optical communication channel 1116 to a destination USBdevice. Unidirectional optical communication channel 1116 mayimplemented using one or more optical fibers. Unidirectional opticalcommunication channel 1116 may be any of unidirectional opticalcommunication channel 114, 116, 118, or 120.

FIG. 12 is a circuit diagram depicting a demodulating circuit 1200.Modulating circuit may be configured to demodulate low-speed signalsfrom a composite signal that includes one or more USB high-speed signalsand the low-speed signals. As depicted, modulating circuit 1200 includesSSRX0+/−terminal 1202, high-speed signal demodulation circuit 1206,average optical power detection circuit 1210, buffer 1208, andphotodetector 1212.

In one aspect, photodetector 1212 receives optical NRZ signal 1122 overunidirectional optical communication channel 1116. Photodetector 1212may convert optical NRZ signal 1122 into a composite signal that has anaverage power modulation in accordance with low-speed signal 1104.High-speed signal demodulation circuit 1206 may demodulate the compositesignal to generate an NRZ electrical signal 1214 that is received bySSRX0+/−terminal 1202. SSRX0+/−terminal 1202 may be similar toSSRX0+/−terminal 206 or 328. NRZ electrical signal 1214 may besubstantially identical to NRZ electrical signal 1118.

In one aspect, average optical power detection circuit 1210 extracts anaverage optical power from the composite electrical signal output byphotodetector 1212, to generate a low-speed electrical signal 1216. Thislow-speed signal 1216 may be amplified by buffer 1208 and output as alow-speed signal 1204 that may be substantially identical to low-speedsignals 1104.

In one aspect, in order to realize the long-distance and lowelectromagnetic radiation transmission of USB signals, the sidebandsignal and channel configuration signal (CC) signals (i.e., thelow-speed USB signals) are transmitted simultaneously with thehigh-speed signals along optical fiber path (i.e., using a singleunidirectional optical communication channel). The specific modulationand demodulation process is low-speed signal modulation and demodulationas shown as performed by a combination of modulating circuit 1100 anddemodulating circuit 1200.

A driving current of laser diode 1114 may be divided into modulationcurrent and bias current. Modulating circuit 1100, the modulation of thehigh-speed signal (i.e., NRZ electrical signal 1118)) uses modulationcurrent while the modulation of low-speed signal 1104 uses a biascurrent of laser diode 1114. In modulating circuit 1100, low-speedsignal 1104 passes through buffer 1108, and laser bias current control1112 modulates the laser bias current. The modulation result is shown inin the output eye diagram (i.e., optical NRZ signal 1122). The change oflow-speed signal 1104 leads to a change of the average optical power ofthe output optical signal (i.e., optical NRZ signal 1122). The averageoptical power is used to detect and demodulate low-speed signal 1104when receiving (i.e., by demodulating circuit 1200).

FIG. 13 is a block diagram depicting an embodiment of a USB opticalconnection interface 1300. As depicted, USB optical connection interface1300 includes USB system 1302, optical connector 1318, and USB system1370. USB system 1302 further includes SSTX0+/−terminal 1304,SSTX1+/−terminal 1306, SSRX0+/−terminal 1308, SSRX1+/−terminal 1310,SBTX terminal 1312, CC terminal 1314, and SBRX terminal 1316. USB system1370 further includes SSTX0+/−terminal 1372, SSTX1+/−terminal 1374,SSRX0+/−terminal 1376, SSRX1+/−terminal 1378, SBTX terminal 1380, CCterminal 1382, and SBRX terminal 1384. Optical connector 1318 furtherincludes two printed circuit boards—PCB 1320 and PCB 1348. PCB 1320further includes EO (electro-optical) interface 1322. PCB 1348 furtherincludes EO interface (electro-optical) 1350. EO interface 1322 furtherincludes SSTX0+/−terminal 1324, SSTX1+/−terminal 1326, SSRX0+/−terminal1328 SSRX1+/−terminal 1330, SBTX terminal 1332, CC terminal 1334, SBRXterminal 1336, EO TX 1338, and EO RX 1340. EO interface 1350 furtherincludes SSTX0+/−terminal 1356, SSTX1+/−terminal 1358, SSRX0+/−terminal1360, SSRX1+/−terminal 1362, SBTX terminal 1364, CC terminal 1366, SBRXterminal 1368, EO TX 1352, and EO RX 1354. EO TX 1338 may be configuredto transmit one or more optical signals to EO RX 1352 via aunidirectional optical communication channel 1342. EO TX 1354 may beconfigured to transmit one or more optical signals to EO RX 1340 via aunidirectional optical communication channel 1346. Each ofunidirectional communication channel 1342 and 1346 may be implementedusing one or more optical fibers.

In one aspect, each of EO interface 1322 and 1350 functions similar toelectro-optical interface 500. Each of EO TX 1338 and EO TX 1354 may besimilar to TX circuit 532. Each of EO RX 1340 and EO RX 1352 may besimilar to RX circuit 534.

Optical connector 1318 optically interconnects USB system 1302 with USBsystem 1370. In one aspect, USB system 1302 is similar to USB system102. USB system 1370 may be similar to USB system 108. In one aspect,the connectivity between USB system 1302 and EO interface 1322, usingterminals SSTX0+/−1304 through SBRX 1316 connected to terminalsSSTX0+/−1324 through SBRX 1336, is similar to the connectivity betweenUSB system 102 and electro-optical interface 104. In one aspect, theconnectivity between USB system 1370 and EO interface 1322, usingterminals SSTX0+/−1372 through SBRX 1384 connected to terminalsSSTX0+/−1356 through SBRX 1368, is similar to the connectivity betweenUSB system 108 and electro-optical interface 104.

In one aspect, EO interface 1322 is integrated onto PCB 1320, and EOinterface 1350 is integrated onto PCB 1348. Essentially, opticalconnector 1318 may be an alternative embodiment of optical connector122, with each of electro-optical interface 104 and electro-opticalinterface 106 integrated onto a separate PCB. In one aspect, each of EOinterface 1350 and 1348 is integrated onto a single integrated circuit(IC or “chip”). Functionally, optical connector 1318 provides an opticalUSB or Thunderbolt interface between USB system 1302 and USB system1370. As depicted, optical connector 1318 uses an NRZ optical signal1344 to communicate along each of unidirectional optical communicationchannels 1342 and 1346, with each unidirectional optical communicationchannel supporting a separate NRZ optical signal.

In one aspect, optical connector 1318 is a two-optical-fiberUSB/thunderbolt active optical cable connected a with USB single-channeldevice at each end (i.e., USB system 1302 and USB system 1370). In oneaspect, each of EO interface 1322 and 1350 is implemented as a distinctintegrated circuit. The respective integrated circuits are bonded ontoPCB 1320 and PCB 1348, respectively. Each of EO TX 1338 and EO RX 1340may be integrated onto PCB 1320, as a laser and photodiode,respectively. In one aspect, each of EO TX 1338 and EO RX 1340 arecovered with optically-transparent lenses. Each of EO TX 1354 and EO RX1352 may be integrated onto PCB 1348, as a laser and photodiode,respectively. In one aspect, each of EO TX 1354 and EO RX 1352 arecovered with optically-transparent lenses.

In one aspect, a USB system interface end of each of PCB 1320 and PCB1348 is assembled into a distinct USB connector. The optical interfaceend of each of PCB 1320 and PCB 1348 may be interconnected by one ormore optical fibers to realize an active optical cable (i.e., opticalconnector 1318) that is compatible with the USB/Thunderbolt protocol.

When the devices at both terminals of optical connector 1318 (i.e., USBsystem 1302 and USB system 1370) are USB3 or USB4 single-channeldevices, optical connector 1318 uses NRZ signals (e.g., NRZ opticalsignal 1344) for communication. In this mode some circuits in opticalconnector 1318 enter power-down mode to save power consumption in amanner similar to the circuits described for electro-optical interface400, modulating circuit 600, and demodulating circuit 700. Opticalconnector 1318 may use two optical fibers (e.g., unidirectional opticalcommunication channels 1342 and 1346) to realize the communicationbetween two terminals of five electrical signals, such as SSTX0+/−,SSRX0+/−, SBTX, SBRX and CC. Optical connector 1318 may be designed tohave low design complexity, low cost, low power consumption, longtransmission distance, good signal quality and good electromagneticcompatibility.

FIG. 14 is a block diagram depicting an embodiment of a USB opticalconnection interface 1400. As depicted, USB optical connection interface1400 includes USB system 1402, optical connector 1418, and USB system1470. USB system 1402 further includes SSTX0+/−terminal 1404,SSTX1+/−terminal 1406, SSRX0+/−terminal 1408 SSRX1+/−terminal 1410, SBTXterminal 1412, CC terminal 1414, and SBRX terminal 1416. USB system 1470further includes SSTX0+/−terminal 1472, SSTX1+/−terminal 1474,SSRX0+/−terminal 1476 SSRX1+/−terminal 1478, SBTX terminal 1480, CCterminal 1482, and SBRX terminal 1484. Optical connector 1418 furtherincludes two printed circuit boards—PCB 1420 and PCB 1448. PCB 1420further includes EO (electro-optical) interface 1422. PCB 1448 furtherincludes EO interface (electro-optical) 1450. EO interface 1422 furtherincludes SSTX0+/−terminal 1424, SSTX1+/−terminal 1426, SSRX0+/−terminal1428 SSRX1+/−terminal 1430, SBTX terminal 1432, CC terminal 1434, SBRXterminal 1436, EO TX 1438, and EO RX 1440. EO interface 1450 furtherincludes SSTX0+/−terminal 1456, SSTX1+/−terminal 1458, SSRX0+/−terminal1460 SSRX1+/−terminal 1462, SBTX terminal 1464, CC terminal 1466, andSBRX terminal 1468, EO TX 1452, and EO RX 1454. EO TX 1438 may beconfigured to transmit one or more optical signals to EO RX 1452 via aunidirectional optical communication channel 1442. EO TX 1454 may beconfigured to transmit one or more optical signals to EO RX 1440 via aunidirectional optical communication channel 1446. Each ofunidirectional communication channel 1442 and 1446 may be implementedusing one or more optical fibers.

In one aspect, each of EO interface 1422 and 1450 functions similar toelectro-optical interface 500. Each of EO TX 1438 and EO TX 1454 may besimilar to TX circuit 532. Each of EO RX 1440 and EO RX 1452 may besimilar to RX circuit 534.

Optical connector 1418 optically interconnects USB system 1402 with USBsystem 1470. In one aspect, USB system 1402 is similar to USB system102. USB system 1470 may be similar to USB system 108. In one aspect,the connectivity between USB system 1402 and EO interface 1422, usingterminals SSTX0+/−1404 through SBRX 1416 connected to terminalsSSTX0+/−1424 through SBRX 1436, is similar to the connectivity betweenUSB system 102 and electro-optical interface 104. In one aspect, theconnectivity between USB system 1470 and EO interface 1422, usingterminals SSTX0+/−1472 through SBRX 1484 connected to terminalsSSTX0+/−1456 through SBRX 1468, is similar to the connectivity betweenUSB system 108 and electro-optical interface 104.

In one aspect, EO interface 1422 is integrated onto PCB 1420, and EOinterface 1450 is integrated onto PCB 1448. Essentially, opticalconnector 1418 may be an alternative embodiment of optical connector122, with each of electro-optical interface 104 and electro-opticalinterface 106 integrated onto a separate PCB. In one aspect, each of EOinterface 1450 and 1448 is integrated onto a single integrated circuit(IC or “chip”). Functionally, optical connector 1418 provides an opticalUSB or Thunderbolt interface between USB system 1402 and USB system1470. As depicted, optical connector 1418 uses a 4-level pulse-amplitudemodulated (PAM4) optical signal 1444 to communicate along each ofunidirectional optical communication channels 1442 and 1446, with eachunidirectional optical communication channel supporting a separate PAM4optical signal.

In one aspect, optical connector 1418 is a two-optical-fiberUSB/thunderbolt active optical cable connected a with USB single-channeldevice at each end (i.e., USB system 1402 and USB system 1470). In oneaspect, each of EO interface 1422 and 1450 is implemented as a distinctintegrated circuit. The respective integrated circuits are bonded ontoPCB 1420 and PCB 1448, respectively. Each of EO TX 1438 and EO RX 1440may be integrated onto PCB 1420, as a laser and photodiode,respectively. In one aspect, each of EO TX 1438 and EO RX 1440 arecovered with optically-transparent lenses. Each of EO TX 1454 and EO RX1452 may be integrated onto PCB 1448, as a laser and photodiode,respectively. In one aspect, each of EO TX 1454 and EO RX 1452 arecovered with optically-transparent lenses.

In one aspect, a USB system interface end of each of PCB 1420 and PCB1448 is assembled into a distinct USB connector. The optical interfaceend of each of PCB 1420 and PCB 1448 may be interconnected by one ormore optical fibers to realize an active optical cable (i.e., opticalconnector 1418) that is compatible with the USB/Thunderbolt protocol.

When the devices at both terminals of optical connector 1418 (i.e., USBsystem 1402 and USB system 1470) are USB3 or USB4 single-channeldevices, optical connector 1418 uses PAM4 signals (e.g., PAM4 opticalsignal 1444) for communication. Optical connector 1418 may use twooptical fibers (e.g., unidirectional optical communication channels 1442and 1446) to realize the communication between two terminals of sevenelectrical signals, such as SSTX0+/−, SSRX0+/−, SSTX1+/−, SSRX1+/−,SBTX, SBRX and CC. Optical connector 1418 may be designed to have lowdesign complexity, low cost, low power consumption, long transmissiondistance, good signal quality and good electromagnetic compatibility.

Some features of the optical connector (i.e., active optical cable)described herein (e.g., optical connector 122, 1318 or 1418) include:

At each port, high-speed signals SSTX0+/− and SSTX1+/− are transferredto two lasers (e.g., VCSELs) for transmission, and two receivingcircuits receive the high-speed signals at an opposite terminal andoutput the signals to SSRX0+/− and SSRX1+/− of local terminals.

The A-terminal interface and the B-terminal interface are configuredwith a transmitting terminal and a receiving terminal, wherein thetransmitting terminal modulates sideband signals and channelconfiguration signals into the same optical path with high-speed signalsfor transmission through time division multiplexing and laser biascurrent modulation, and the receiving terminal separates low-speedsignals by using an average optical power detection circuit and drivesthe sideband signals and channel configuration signals of oppositeterminals through time division multiplexing.

The A-terminal interface and the B-terminal interface of the activeoptical cable of the system are symmetrical, and the active opticalcable has no directionality;

At each port, high-speed signals SSTX0+/−, SSTX1+/− are modulated intothe same laser for transmission; and in dual-channel communication, twopaths of high-speed signals are modulated into PAM4 signals, while insingle-channel communication, high-speed signals are transmitted by NRZcoding, the receiving terminal selects PAM4 demodulation or NRZdemodulation according to channel configuration and then outputs thesignals to SSRX0+/−, SSRX1+/− of local terminals.

A monitoring unit filters out high-speed signals through a filter toobtain LFPS signals, and the filtered signals are subjected to envelopelength detection and idle time detection to obtain burst time and repeattime of LFPS signals, and LFPS instructions are obtained by using bursttime and repeat time look-up tables;

Simultaneously, LFPS signals at both terminals are monitored to judge anegotiation result of devices at both sides; when there is only Pollingsignals at one terminal instead of SCD1 and SCD2 signals during LFPSnegotiation, it means that the device is a USB3.0 device and onlysupports single channel mode;

If both communication parties (e.g., USB system 102 and USB system 108)use SCD1 and SCD2 signals for negotiation, it means that the device is aUSB3.1 or USB3.2 device, and LBPM signals are further analyzed; if LBPMsignals only contains rate information but do not contain channelconfiguration information, the device is USB3.1 device, andcommunication is in single channel mode;

If LFPS-based PWM message (LBPM, where PWM stands for “Pulse WidthModulation”) information contains channel configuration information, itis judged according to the negotiation of channel configurationinformation at both terminals, and the configuration of the party with alow channel number in the negotiation is taken as the channelconfiguration;

When a USB device (e.g., USB system 102 or 108) is a USB4 device, thereis no LFPS signal in a high-speed channel; when a USB3 adapter exists inUSB4, LFPS signals are converted into a special packet for transmission,and the channel configuration negotiation of USB4 is mainly conductedthrough sideband communication.

The monitoring unit simultaneously monitors sideband signals of thetransmitting terminal and the receiving terminal to judge thenegotiation result of channel configuration between the two terminals,

The signals of SBTX and SBRX are amplified, and a sideband signal packetis analyzed to obtain the analysis of sideband communication. Themonitoring unit extracts read-write information of channel configurationrelated registers in the sideband signal packet, and obtains a channelconfiguration negotiation result, with the lowest channel number in bothterminals of communication as a channel negotiation result;

When the device is plugged in, the sideband signals are detected first,and if there are sideband signals, a monitoring decision for sidebandsignal negotiation is configured as single-channel or dual-channel;

If there is no sideband signal, LFPS negotiation monitoring isperformed;

If there are data errors and other abnormalities in the monitoringprocess, the process returns to an initialization state forre-monitoring.

In one aspect, optical connector 122 provides two specific transmissionmodes: four-optical-fiber transmission of USB protocol and thunderboltprotocol signals, and two-optical-fiber transmission of USB protocol andthunderbolt protocol signals. In both transmission modes, the channelconfiguration results of a USB device connected to both terminals areobtained by monitoring LFPS signals and sideband signals, and theoperation is adaptively selected to be single-channel mode ordual-channel mode. In dual-channel mode, all modules work, while insingle-channel mode, some modules are automatically turned off forlow-power operation.

On the basis of the idea of optical fiber transmission of USB protocoland Thunderbolt protocol signals, optical connector 122 implements amethod of compressing out-of-band signals, channel configuration signals(CC) and high-speed signals into the same optical fiber fortransmission. Optical connector also implements a transmission method ofadaptive switching channel configuration (idle channel with low powerconsumption) or adaptive switching channel modulation and demodulationcoding, by monitoring LFPS signals (low frequency periodic signals) orout-of-band signals when working in two-channel sideband single-channelmode. With low design and manufacturing complexity, high integration,low power consumption and low cost, the system provided by theapplication realizes optical fiber transmission compatible with USB3,USB4 and thunderbolt protocols.

FIG. 15 is an example flow diagram depicting a method 1500 to performUSB communication. Method 1500 may include detecting a presence of a USBsideband signal over an optical communication link (1502). For example,sideband signal monitoring unit 900 may detect a presence of a USBsideband signal received over unidirectional optical communicationchannel(s) 448 and/or 450. 1502 may correspond to state 1004 of stateflow 1000.

Method 1500 may include determining that the USB communication requestcorresponds to a USB communication mode (1504). For example, sidebandsignal monitoring unit 900 may determine that the USB communicationrequest corresponds to a USB communication mode. In one aspect, the USBcommunication mode is a USB4 communication mode.

Method 1500 may include performing a sideband negotiation (1506). Forexample, sideband signal monitoring unit 900 may perform a sidebandnegotiation. 1506 may correspond to state 1006 of state flow 1000.

Method 1500 may include enabling the USB communication mode (1508). Inone aspect, the USB communication mode is a USB4 communication mode thatmay be enabled by sideband signal monitoring unit 900. Sideband signalmonitoring unit 900 may also analyze USB sideband signals to determinewhether USB communication is being performed in a USB3 mode or aUSB4/Thunderbolt mode, and enable the appropriate USB communicationmode.

Method 1500 may include determining a specified number of channelsassociated with the USB communication request (1510). For example,sideband signal monitoring unit 900 may determine whether the USBcommunication request pertains to single-channel communication ordual-channel communication.

Method 1500 may include performing USB communication using the specifiednumber of channels (1512). For example, USB communication may beperformed by electro-optical interface 500 in a dual-channelconfiguration (state 1012), or in a single-channel configuration (state1014).

FIG. 16 is an example flow diagram depicting a method 1600 to performUSB communication. Method 1600 may include failing to detect a presenceof a USB sideband signal received over an optical communication channel(1602). For example, sideband signal monitoring unit 900 may fail todetect a presence of a USB sideband signal received over unidirectionaloptical communication channel(s) 448 and/or 450. 1602 may correspond tostate 1004 of state flow 1000.

Method 1600 may include detecting a presence of an LFPS signal receivedover the optical communication channel (1604). For example, LFPS signalmonitoring unit 800 may detect a presence of an LFPS signal in areceived USB signal.

Method 1600 may include determining that the USB communication requestcorresponds to a USB communication mode (1606). For example, LFPS signalmonitoring unit 800 may determine that the USB communication requestcorresponds to a specific USB communication mode. In one aspect, the USBcommunication mode is a USB3 or other USB legacy protocol communicationmode.

Method 1600 may include performing an LFPS test (1608). For example,LFPS signal monitoring unit 800 may test an existence of one or moreLFPS signals in the USB communication signals. This enables monitoringunit 800 to distinguish between an LFPS signal and a high-speed USBcommunication signal. 1606 and 1608 may correspond to state 1008.

Method 1600 may include enabling the USB communication mode (1610). Inone aspect, the USB communication mode is a USB3 or other legacy USBcommunication mode that may be enabled by LFPS signal monitoring unit800. Sideband signal monitoring unit 900 may also analyze USB sidebandsignals to determine whether USB communication is being performed in aUSB3 mode or a USB4/Thunderbolt mode, and enable the appropriate USBcommunication mode.

Method 1600 may include determining a specified number of channelsassociated with the USB communication request (1612). For example, LFPSsignal monitoring unit 800 may determine whether the USB communicationrequest pertains to single-channel communication or dual-channelcommunication.

Method 1600 may include performing USB communication using the specifiednumber of channels (1614). For example, USB communication may beperformed by electro-optical interface 500 in a dual-channelconfiguration (state 1012), or in a single-channel configuration (state1014).

In some aspects, methods 1500 and 1600 collectively implement state flow1000.

FIG. 17 is an example flow diagram depicting a method 1700 to performUSB optical communication. Method 1700 may include receiving one or moreUSB electrical communication signal to be transmitted to a receiver(1702). For example, electro-optical interface 500 may receive a USBelectrical signal (e.g., an SSTX0+/− or a combination of an SSTX0+/− andan SSTX1+/−signal, and other USB signals such as an SBTX signal, and oneor more CC signals) from USB system 102 for transmission toelectro-optical interface 106.

Method 1700 may include analyzing the USB electrical communicationsignals (1704). For example, monitoring unit 526 may analyze the USBelectrical communication signals.

Method 1700 may include determining whether the USB communicationsignals are to be transmitted in a single-channel mode or in adual-channel mode (1706). For example, monitoring unit 526 may determinewhether the USB communication signals are to be transmitted in asingle-channel mode or a dual channel mode.

If the USB communication signals are to be transmitted in asingle-channel mode, then method 1700 goes to 1708, which may includegenerating an NRZ electrical signal corresponding to the USB electricalcommunication signal. For example, electro-optical interface 500 maygenerate an NRZ signal comprised of an SSTX0+/−signal with average powermodulated by any combination of an SSTX and one or more CC signals.

Method 1700 may include converting the NRZ electrical signal into an NRZoptical signal (1710). For example, an output from laser bias currentmodulator 520 may be converted to an NRZ optical signal by TX circuit532.

Method 1700 may include transmitting the NRZ optical signal to thereceiver over an optical communication channel (1712). For example, TXcircuit 532 may transmit the NRZ optical signal via unidirectionaloptical communication channel to the corresponding electro-opticalinterface at the other end of optical connector 122. In thesingle-channel mode, some components of electro-optical interface may bepowered down to enable a power savings feature.

If the USB communication signals are to be transmitted in a dual-channelmode, then method 1700 goes from 1706 to 1714, which may includegenerating a PAM4 electrical signal corresponding to the USB electricalcommunication signal. For example, electro-optical interface 500 maygenerate a PAM4 signal comprised of an SSTX0+/− and an SSTX1+/−signalwith average power modulated by any combination of an SSTX and one ormore CC signals.

Method 1700 may include converting the PAM4 electrical signal into aPAM4 optical signal (1716). For example, an output from laser biascurrent modulator 520 may be converted to a PAM4 optical signal by TXcircuit 532.

Method 1700 may include transmitting the PAM4 optical signal to thereceiver over an optical communication channel (1718). For example, TXcircuit 532 may transmit the PAM4 optical signal via unidirectionaloptical communication channel to the corresponding electro-opticalinterface at the other end of optical connector 122.

Although the present disclosure is described in terms of certain exampleembodiments, other embodiments will be apparent to those of ordinaryskill in the art, given the benefit of this disclosure, includingembodiments that do not provide all of the benefits and features setforth herein, which are also within the scope of this disclosure. It isto be understood that other embodiments may be utilized, withoutdeparting from the scope of the present disclosure.

What is claimed is:
 1. A method comprising: receiving one or more USBelectrical communication signals; analyzing the one or more USBelectrical communication signals determining a channel transmission modeassociated with the one or more USB communication signals, the channeltransmission mode selected from among: a single-channel mode or adual-channel mode; responsive to analyzing the one or more USBelectrical signals: generating a channel transmission mode electricalsignal specific to the channel transmission mode and corresponding tothe USB electrical communication signals; converting the channeltransmission mode electrical signal into a corresponding channeltransmission mode optical signal; and transmitting the channeltransmission mode specific optical signal to the receiver over anoptical communication channel.
 2. The method of claim 1, whereindetermining a channel transmission mode comprises determining asingle-channel mode; wherein generating a channel transmission modeelectrical signal comprises generating an NRZ electrical signal; andwherein converting the channel transmission mode electrical signal intoa corresponding channel transmission mode optical signal comprisesconverting the NRZ electrical signal to an NRZ optical signal.
 3. Themethod of claim 2, wherein the NRZ electrical signal is associated withtwo signal levels.
 4. The method of claim 1, wherein determining achannel transmission mode comprises determining a dual-channel mode;wherein generating a channel transmission mode electrical signalcomprises generating an PAM4 electrical signal; and wherein convertingthe channel transmission mode electrical signal into a correspondingchannel transmission mode optical signal comprises converting the PAM4electrical signal to a PAM4 optical signal.
 5. The method of claim 4,wherein the PAM4 electrical signal is associated with four signallevels.
 6. The method of claim 1, wherein the optical communicationchannel is comprised of one or more optical fibers.
 7. The method ofclaim 1, wherein converting the channel transmission mode electricalsignal into a corresponding channel transmission mode optical signal isperformed by a VCSEL.
 8. The method of claim 1, further comprisingconverting one or more USB optical communication signals into the one ormore USB electrical signals.
 9. The method of claim 8, wherein theconverting is performed by a VCSEL.
 10. A method comprising: receivingone or more USB optical communication signals over an opticalcommunication channel; converting the one or more USB opticalcommunication signals into electrical communication signals; analyzingthe one or more USB electrical communication signals determining achannel reception mode associated with the one or more USB communicationsignals, the channel reception mode selected from among: asingle-channel mode or a dual-channel mode; and responsive to analyzingthe one or more USB electrical signals, decoding the USB electricalcommunication signals specific to the channel transmission mode.
 11. Themethod of claim 10, wherein the channel reception mode optical signal inthe single-channel mode is an NRZ optical signal.
 12. The method ofclaim 11, wherein the NRZ optical signal is associated with two signallevels.
 13. The method of claim 10, wherein the channel reception modeoptical signal in the dual-channel mode is a PAM4 optical signal. 14.The method of claim 13, wherein the PAM4 optical signal is associatedwith four signal levels.
 15. The method of claim 10, wherein theconverting is performed by a photodetector.
 16. The method of claim 15,further comprising amplifying an output of the photodetector.
 17. Themethod of claim 16, wherein the amplifying is performed by a lineartransimpedance amplifier.
 18. The method of claim 10, wherein theoptical communication channel is comprised of one or more opticalfibers.